- For other uses of "Killer Frost", see Killer Frost (disambiguation).
- "The things we see, the things that we face, no one can do this alone. Trying is the biggest mistake that you can make."
- —Caitlin Snow to Barry Allen[src]
Dr. Caitlin "Cait" Snow, M.D. (born February 28, 1989) is a bio-engineer at S.T.A.R. Labs and a former scientist at Mercury Labs. She was working during the particle accelerator disaster and tended to Barry Allen during his coma with Cisco Ramon until he woke up. After he began his crusade as "The Flash" Caitlin became a member of his team with Cisco and Dr. "Harrison Wells", before discovering the latter's true identity as Eobard Thawne, and provides medical support for the team. Caitlin is the daughter of the late Dr. Thomas Snow and Dr. Carla Tannhauser, the widow of the late Ronnie Raymond, and close friends with Cisco, Barry, Felicity Smoak, Kara Danvers, the late professor Martin Stein, Iris West-Allen, and Ralph Dibny. She is also the former lover of "Jay Garrick", before discovering his true identity as Hunter Zolomon, and the ex-girlfriend of Julian Albert.
In the Flashpoint timeline, Caitlin is not a scientist but a doctor who is unwillingly brought into Ramon Industries by Barry to help him restore the timeline. Following Barry's attempt to restore the timeline, Caitlin is once again a scientist at S.T.A.R. Labs, but she is also a meta-human with abilities similar to her Earth-2 doppelgänger, who she is afraid of becoming like. However, it was later revealed that she was a dormant meta-human all along due to her father using an experimental ALS treatment on her, when she was 10. After being taken over by her rising anger while using her meta-human powers and losing control of her emotions, Caitlin briefly started going by her doppelgänger's name, Killer Frost.
After suffering a clinical death from a seizure and subsequently being revived by her regenerative powers, her biochemistry was altered, culminating in her becoming fully consumed by her anger as Killer Frost, later encountering and allying with Savitar after the proclaimed speedster god reveals his true identity as a future version of Barry Allen. Later, between Cisco giving Caitlin the choice to cure herself rather than force it on her and watching Savitar nearly kill him, Caitlin finally regained her true personality and control of her powers. Despite this, Caitlin decided not to take the cure. Feeling lost to her own identity, Caitlin left Team Flash on good terms to rediscover herself. Six months later, having seemingly come to terms with her mistakes as Killer Frost, Caitlin finally decided to re-join Team Flash, only to discover that her Killer Frost-side had returned.
Shortly after returning to Team Flash, Caitlin once again began to struggle with her Killer Frost side and eventually lost control. Iris convinced both Caitlin and Killer Frost that they could try to be the same person instead of choosing one life or the other. As such, when preparing to serve as back up to Barry along with Cisco, she stated "Snow and Frost standing by", emphasizing that both Caitlin and Killer Frost were prepared to work together to help. When Nazis from Earth-X tried to invade Earth-1, she aided her friends in the battle that followed, earning Mick Rory's affection. In a battle against Clifford DeVoe, she lost her Killer Frost side as a result of DeVoe using Dominic Lanse's powers to create a mental block. After defeating Siren-X from Earth-X, Caitlin discovers that Killer Frost is still inside her, without the presence of dark matter. She later learns, from a suppressed memory, that Killer Frost has been with her since childhood, before she was exposed to the dark matter released by the particle accelerator.
After defeating DeVoe and getting Ralph back, she discovered that her father's death certificate was a fake and that he was actually alive. Barry, Cisco and Caitlin eventually found him hiding out in an old warehouse. However, he later revealed himself to be Thomas' evil alternate personality and attempted to kill the team and take over Thomas' body completely. During the fight, Caitlin managed to break through the mental block that DeVoe had created and regain Killer Frost. By late 2019, she'd begun referring to her alternate persona simply as "Frost".
Eventually, Caitlin and Frost are affected by exposure to the Mirror Monarch's rays; causing Frost's cells to replicate enough to create a new body and also separating their telepathic connection.
- 1 Biography
- 1.1 Original multiverse
- 1.1.1 Early life
- 1.1.2 Working under Harrison Wells
- 1.1.3 Working with The Flash
- 1.1.4 Zoom's arrival
- 1.1.5 Becoming evil
- 1.1.6 Joining Savitar
- 1.1.7 Rediscovery and return
- 1.1.8 Barry's incarceration
- 1.1.9 Searching for her father and recovering Killer Frost
- 1.1.10 Meeting an old colleague
- 1.1.11 Anti-Monitor Crisis
- 1.1.12 Erased future
- 1.2 New multiverse
- 1.1 Original multiverse
- 2 Personality
- 3 Powers and abilities
- 4 Equipment
- 5 Appearances
- 5.1 Arrow
- 5.2 The Flash
- 5.3 Supergirl
- 5.4 DC's Legends of Tomorrow
- 5.5 Stretched Scene
- 5.6 Freedom Fighters: The Ray
- 5.7 Comics
- 5.8 Novels
- 5.9 The Chronicles of Cisco
- 6 Gallery
- 7 Trivia
- 8 Behind the scenes
- 9 References
Caitlin Snow was born on February 28, 1989 to scientists Thomas Snow and Carla Tannhauser. From a young age, she idolized her parents and was inspired to follow in their footsteps. As a child, Caitlin practiced the Hippocratic Oath and was apparently obsessed with it, growing to value life so much that she refused to let anyone even step on a bug if she could help it.
Caitlin was very close to her father; on Christmas, they would watch old holiday movies together as it snowed for hours without end outside. Thomas personally mentored Caitlin in multiple fields of science and the two partook in various educational activities together for their own entertainment. However, Caitlin's father later fell ill, suffering from multiple sclerosis. During this period, Thomas realized that Caitlin had inherited his gene for ALS and used experimental cryogenic therapy to save her by freezing the progression of the disease, just as he'd done for himself. While the experimental trials successfully cured Caitlin, they left her with a dormant cryokinetic-powered alternate personality, who would later be known as Killer Frost.
One day, Caitlin was out riding her bicycle with her father when she fell off and got her leg stuck in the bike as a car sped towards her. Her resulting injuries and fear caused Killer Frost to manifest for the first time, triggering Caitlin's transformation into her alter-ego. Despite her father's protests, Caitlin looked into her bicycle mirror and saw her transformation, causing her to scream in terror. Caitlin would repress this memory and Killer Frost for years.
At some point following this, Thomas apparently died from ALS when Caitlin was 10 years old, much to her and her mother's heartache. After Thomas' death, Carla began focusing only on her work as a way to cope with the pain, and her subsequent neglect of Caitlin left them estranged for years.
Caitlin was a bright pupil and studied at fine learning institutions through her own merit. As an adult, she became a trained scientist and neurosurgeon. Despite their estrangement, Carla offered Caitlin a position at the former's research company, Tannhauser Industries, but Caitlin wanted to make a name for herself and declined. Sometime before 2011, Caitlin moved to Central City, where she did her residency at Central City General Hospital. During this time, Caitlin studied under Dr. Rachel Rosso and worked with her son, Ramsey Rosso, becoming close to them. Rachel sent a letter of recommendation for her to S.T.A.R. Labs, leading Caitlin straight to her dream career.
Working under Harrison Wells
Joining S.T.A.R. Labs
Caitlin was later hired at S.T.A.R. Labs by Dr. "Harrison Wells", where she met Ronnie Raymond, a structural engineer. In contrast to Caitlin's guarded personality, Ronnie was open and outgoing, and would later describe them as being like "fire and ice". In spite of their very different natures, Caitlin and Ronnie fell deeply in love and started dating. Upon getting together, the two found they had trouble communicating at work, so they attended couples counseling for a time. Though Caitlin enjoyed working at S.T.A.R. Labs, she, like most employees, was often irritated by Dr. Wells' protégé, Hartley Rathaway.
Around 2012, Caitlin went out of town with Ronnie for their one-year anniversary. Before leaving, she met newly-employed engineer, Cisco Ramon, after witnessing him debate engineering with Hartley. Cisco and Caitlin became close friends to the point where he would consider Caitlin and Ronnie family, being estranged from his own, and looked up to the couple.
At one point, the S.T.A.R. Labs team was under a strict deadline working on the particle accelerator. Caitlin, Cisco, and Ronnie were struggling, working late at night on the iridium plating for the synchotron, and they could not get the dubnium capacitor to hold a single charge. Eventually, Ronnie lost his calm demeanor and yelled, "Come on, you dumb-nium capacitor! Take charge!"
In 2013, Caitlin and Ronnie visited Piedmont State Park where in front of the Hudson Falls, Ronnie proposed to Caitlin and she accepted.
Over the years, Caitlin grew increasingly distant from her mother; the two didn't visit each other or talk much, and Caitlin apparently never even told Carla about Ronnie.
The particle accelerator explosion
Caitlin was working on the night that the S.T.A.R. Labs particle accelerator was to be switched on. She and her fiancée, Ronnie, were discussing their honeymoon when they were alerted of the impending switching on. Dr. "Harrison Wells" paused for a moment and walked into the hall, and when Cisco and Caitlin came to check on him, he asked Caitlin to retrieve the bottle of Dom Pérignon they had been saving.
After he switched it on, "Wells" went to make a toast, but it was soon made apparent that the particle accelerator was malfunctioning. Being the structural engineer, Ronnie had to go down with Cisco Ramon to try to, if not repair it, contain the blast. Despite her hesitation, he had to go. After he didn't come back in a while, Caitlin went down to talk to him. However, Ronnie had had Cisco put the accelerator into lock-down, locking him inside the core chamber. Caitlin and Ronnie talked, but before they could continue, Ronnie's connection was lost, and he was seemingly killed inside the chamber, greatly upsetting Caitlin.
Following an accident involving lightning striking him, Barry Allen was put in a coma. After his situation got critical, he was moved to S.T.A.R. Labs, where he was stabilized and looked after by Caitlin and Cisco. Sometime following this, the two met Felicity Smoak during one of her visits to see the patient.
Time in Starling City
A little while later, Caitlin and Cisco were asked to pack up a S.T.A.R. Labs warehouse in Starling City, following the massive explosion that occurred in Central City. The two were doing an inventory count, discussing the particle accelerator's explosion when they heard movement in the warehouse. They went to investigate, only to find a security guard standing there. Cisco assured him that they were almost done, though he just stared them down, creeping him out. Before the man could reply, he spat blood out and dropped to the ground, with Deathstroke ready behind him. The two made a run for it, managing to incapacitate Deathstroke momentarily with an old energy gun made by Arthur Light. They later reported the incident. Sometime after, they met Felicity Smoak and John Diggle at the hospital. Felicity asked about Barry's condition, and Caitlin told her how it was still the same. Cisco quickly blurted out that "Iris" had been visiting him a lot. When Felicity asked who Iris was, Cisco struggled to explain their relationship, causing Felicity to walk off, distressed that "Barry's in a coma, he's already moved on". A little while later, Felicity met Cisco and Caitlin again in a lab with a vial of Mirakuru, telling them that she needed their help and that it would be their little secret. Caitlin and Cisco successfully created a cure for the Mirakuru, which would be used by Team Arrow to defeat the Mirakuru-enhanced soldiers during Slade's siege of the city, as well as cure Roy Harper of his unstable condition.
Working with The Flash
Nine months after he was struck by lightning, Barry awoke from his coma to Lady Gaga's "Poker Face", a song he allegedly liked. Cisco called "Dr. Wells" down to the lab as quickly as possible, and explained to Barry what had happened, introducing him and Caitlin. The two took a break as Wells showed Barry around S.T.A.R. Labs, explaining in depth what had actually happened. Later, after discovering that he had the ability to run at super-speed, the team of four headed down to an airfield. After Barry commented on her lack of smiling, she admitted that it felt like the best course of action considering what she'd been through. As Cisco monitored Barry's speed, Caitlin measured his energy output, amazed at how fast he could run, before colliding with some water barrels. They headed back to S.T.A.R. Labs where Wells and Barry discussed the potential for the existence of other people like him, specifically another who had super speed like Barry, though Harrison was certain that Barry was unique. Barry left to meet Iris. After an encounter with Clyde Mardon's weather manipulation, he returned to S.T.A.R. Labs where he was angry at Wells for lying to him in regards to meta-human abilities. Barry returned later, sorry, offering an apology in return for Cisco and Caitlin's help in catching rogue meta-humans. They agreed to help, and Cisco revealed a suit he'd designed for use by firefighters, which he believed would fit Barry's needs perfectly. Barry donned the suit and headed out to where they pinpointed Mardon to be. Cisco and Caitlin communicated with Barry, giving support. When Barry began to attempt to unravel it, Cisco stated his belief that Barry could withstand the pressure, though Caitlin didn't believe Barry himself would. However, after motivation from Dr. Wells, he eventually did.
After a run-in with a strongman at the Central City National Bank, Barry arrived back at S.T.A.R. Labs with a wrongly-healed ankle, after having previously broken it. They decided to re-break it, and Caitlin suggested to run extra tests to make sure that there was no further damage. Following that, Caitlin and Cisco tagged along with Barry to grab some DNA samples from the crime scene at which the strongman had been. While analyzing the sample, they helped Barry find a group of chimpanzees that had escaped from the Central City Zoo. As he locked them up, they revealed that the DNA sample was that of Joey Rose, a former strongman at the Central City Circus. They delved deeper into the closed circus, discovering that its owner had escaped from Belle Reve and killed several people. They notified Barry of this, while Dr. Wells also provided some details he knew on Mr. Bliss from having attended the circus previously, and Barry left to find the circus. Having been gone for a while, Cisco and Caitlin took a truck and crashed through the tent of the circus. Cisco grabbed Barry and Caitlin attempted to drive away, however, their truck was lifted up by Joey Rose, who threw it some distance from the circus tent. As they crawled from the wreckage, they encountered the snake lady. The lady promised to let them pass, but Caitlin believed it to be a trap. The lady assured her that she was genuine, as they were only compliant with Mr. Bliss otherwise torture would be inflicted on them. Before leaving, Caitlin asked what all of it was about, but the woman was only aware that something big was happening. They headed back to S.T.A.R. Labs, where Caitlin explained what had happened to Barry and Cisco further explained what the snake lady had told them. Caitlin suggested that she could experiment with psychotropic drugs on Barry, though she was unsure how he would react. Noticing that Mr. Bliss had arrived at a Central City Cougars match, Dr. Wells urged that they go down to warn everyone. Having destroyed the work van, they took Cisco's car, which Caitlin found unhygienic and tiny. As they arrived, they noticed that The Flash had already evacuated everyone. Iris greeted them and they claimed to be there for the circus.
Caitlin walked in on Cisco as he guided Barry towards a burning building to save people inside. Once he had saved everyone, she ordered him back to S.T.A.R. Labs. Though he tried to justify what he was doing, using his abilities for good, she mentioned that they had actually agreed to locate and contain meta-humans together. Not being able to get her message across, she had Dr. Wells try to help communicate it. She angrily told Barry that she couldn't fix him every time something broke before walking off. After later fainting, Barry headed to S.T.A.R. Labs, where Caitlin yelled at Barry for keeping it to himself, as he could have suffered from a mini-stroke. They decided to test his vitals while he ran on a modified treadmill. They noted his low glucose levels, but not before he fell off and hit the padding. They hooked him up to 40 IV bags in order to bring him back to normal. When he awoke they explained what they determined to be the problem: he hadn't been eating enough for his massive metabolism. Shortly following, Joe appeared through the doors. He began to get angry at Barry for acting as a hero, and Caitlin agreed with his reasoning before Joe left upset. Yet again Barry later returned to S.T.A.R. Labs, having had a run-in with a meta-human who could duplicate himself, who they found to be Danton Black. From some of the perp's blood on Barry's suit, Caitlin was able to speed up the replicating process, making a clone from cells. The clone came to life, freaking Caitlin out, though Joe had returned, shooting the clone. They figured that Danton Black had activated some clones, thus the clone's movement and Barry suited up to head to Stagg Industries. The team provided support to Barry as per usual, Caitlin suggesting to locate the prime in order to take them all out. Barry ultimately beat Danton, who fell to his death. They soon watched a report about it on the news. Barry assured that the three of them were always with him, and that really all of them had been struck by lightning, not just Barry, at least in the metaphorical sense.
A while later, Cisco and Caitlin alerted Barry to a man with a gun in a getaway car being chased by cops, who Barry sped to and placed in the cop car within a matter of seconds. The following day, after the Darbinyan crime family were gassed to death by a presumed meta-human, the S.T.A.R. Labs team began researching what they could, all of them excited by the potential prospects. Joe noted that they would have to find somewhere to hold them, as Iron Heights was less than ideal, and Cisco suggested the particle accelerator. Not wishing to go down, Barry suggested she tag along with him to identify the poison gas. At the CCPD, they headed upstairs. On the way, they were joined by Barry's boss, Captain Singh. Caitlin claimed to be Barry's personal physician. Once they were in the lab waiting for the gas' test results, they discussed Caitlin's late fiancé Ronnie. Once they got the test results, they were intrigued to find two separate tissue samples in it, rather than just one, coming to the conclusion that the meta-human could, in fact, turn into gas himself, hence why his genetic residue was left behind. Barry left to find the meta-human after hearing news on a police radio, leaving Caitlin at the lab. He eventually found the man but inhaled some of the gas. He returned to S.T.A.R. Labs where Caitlin used a needle to painfully extract the gas before it killed him. Once he woke up, Barry apologized for leaving so suddenly, but Caitlin reassured him that it was fine and he had just reminded her of Ronnie. Barry related the story of his mother's death and offered to go into the core chamber with Caitlin to conquer her fears. While they were there, he promised her that Ronnie was a true hero. They were called back up where they were shown the molecular makeup of the poison gas, hydrogen cyanide mixed with a sedative. Barry recalled that executions used those particular chemicals and Caitlin uncovered Kyle Nimbus, who would have been executed at the time of the particle accelerator explosion. She further went on to look up who caught him, Detective West, figuring that he was his final target. Caitlin gave him an antidote to the toxin, and Barry sped to Iron Heights Prison to protect Joe. The team supported Barry, and once he had lured Nimbus out into the open, Caitlin reminded him not to breathe any gas in (as he'd used the antidote on Joe). Finding it too difficult to outrun him, Caitlin suggested to simply have him continue running at Barry to sap his strength, forcing him to revert to human form. Finally capturing The Mist, as Cisco proudly nicknamed him, they put him in the makeshift particle accelerator prison they'd engineered. Cisco attempted to apologize for the night of Ronnie's death, however, Caitlin admitted that she was okay, as she was even more proud of Ronnie. The two-headed out to the cinemas, followed by ice cream.
Caitlin played Barry in a game of Operation while Barry was also played a game of Chess with Harrison Wells, and a game of Ping pong with Cisco while Barry was testing his ability to multitask. When Felicity arrived at S.T.A.R. Labs, Caitlin was pleased to see her again though she was worried that she would know too much of their operation. Caitlin was told that she wouldn't need to worry after being told Felicity works with The Arrow. After the cold gun was stolen, Caitlin along with Harrison learned that Cisco built a weapon that was powerful enough to stop Barry, despite his speed. After Barry was struck by the cold gun, Caitlin noted that Barry's nerve cells would've been damaged permanently had they not regenerated at the speed they did. When Cisco told Barry he built the cold gun to stop him, Caitlin defended Cisco that he was only taking precautions and that it was when Barry was still in a coma. Caitlin was later shocked when Felicity managed to track down Leonard Snart/Captain Cold in a matter of seconds. When Caitlin and Cisco were advised by Felicity to follow Barry and help him, Caitlin reminded Felicity that Barry wanted to be alone. Caitlin was told by Felicity that when someone asks to be alone, that is the best time to help them. Caitlin, along with Cisco and Felicity brought the S.T.A.R. Labs vacuum cleaner, claiming it was the prototype cold gun four times more powerful than the one Leonard had to threaten Snart into backing down.
Barry took Caitlin and Cisco to a social gathering with Iris and Eddie Thawne, who she expressed an attraction, but Barry told her he couldn't get drunk so she took a sample of his blood in a syringe, which she kept in her bag, but Barry was soon called to a bombing in a building where a man was hanging for his life. Later Barry went to find the bomber Sgt. Bette Sans Souci but returned moments later without his suit, after Caitlin desperately tried to get back in contact with him over communications, stating that Bette destroyed it causing it to explode with a single touch. Flash managed to bring Bette back to the lab where Caitlin was able to figure out that the dark matter of the particle accelerator merged with a piece of shrapnel where she got her powers, and later observed as Bette tested her powers. Bette told everyone that she was being targeted by her commanding officer Gen. Wade Eiling and Caitlin tried to find a way to remove her powers but discovered that there was no means of reversing it and though Barry wanted her to stay, become a member of the team, everyone including Caitlin feared she would eventually unintentionally destroy the lab and they needed to avoid being Eiling's enemy. After Bette was killed by Eiling, Barry became slightly depressed and Caitlin tried to cheer him up by making note of his power to walk on water and later made a whiskey shot strong enough for Barry to feel.
As Caitlin and Cisco debated how many insects Barry swallows while running, Barry came to S.T.A.R Labs with a broken hand caused by meta-human Tony Woodward, Barry's childhood bully, which Caitlin tended to but noted that 13 bones were broken in his hand alone, in addition to multiple injuries in the rest of his body. She later watched as Barry practiced fighting on a robotic dummy and dislocated his shoulder and Caitlin tried to fix it but when she asked if Barry was visiting Iris as the Flash again, he lied promoting Caitlin to fix his shoulder by brutally snapping it back in place with her hands. Caitlin and Cisco later deduced where Tony was hiding out, but when Barry was seriously wounded Caitlin and Cisco had to go find him themselves and bring him back to the lab. Cisco and Dr. Wells both agreed that Barry could defeat Tony if he hit Woodward at just the right angle at a speed just over Mach 1, which would require a clear shot 5.3 miles away from his target. Caitlin, on the other hand, begged him not to as it would shatter every bone in his body if done wrong. Later Barry engaged Tony again after the latter had kidnapped Iris, and after getting hurt he ran out, only to stop 5.3 miles away from Woodward, turn around and run at a minimum speed of 837 miles per hour, which Caitlin begged him not to do but nerveless he succeeded. Caitlin watched as Barry confronted Tony, face to face, and was amused by Cisco's desire to stop his own childhood nemesis next.
When Caitlin was walking in the parking lot after she met up with Jason Rusch to learn more about F.I.R.E.S.T.O.R.M., she was kidnapped, due to her association with The Flash, by Leonard Snart and Mick Rory before she could get into her car. Captured, Rory tied her to a chair and gagged her. She was later rescued by Cisco and Joe West.
Discovering Wells' true identity
The team learned of Eobard's plan, to have Barry run fast enough to create a wormhole in which Eobard could return home while Barry could save his mother from Eobard in the first place thus restoring the timeline to order. Caitlin thought the concept was an easy choice until Professor Stein elaborated that Nora's murder had subsequently altered the timeline and changed history, so, therefore, nothing would ever be the same and no one would know because they'd never remember it, meaning Barry may never meet any of them. After tending to Ronnie's wounds from his battle with Reverse-Flash he told her that he and Stein are there to stay for good, and asks if she would like to finally marry him and she said yes. Later the two decided to marry before Barry time-travels in case everything does change and they, with Professor Stein as their rabbi, said their vows and married.
When Eobard was to travel back to the future Barry surprisingly returned and sabotaged his time sphere, forcing Caitlin and Ronnie to manually turn off the generators to close the wormhole before it could grow into a singularity. They succeeded, but, as a result of a paradox from Eddie killing himself to erase Eobard from existence, the wormhole reopened, and the team was helpless to watch it grow and begin consuming everything in Central City before it would eventually consume the world. Flash sped off into the portal to close it and managed to stabilize its range but wasn't able to close it. Professor Stein informed Ronnie the only way to destroy it would be for them, as Firestorm to separate inside it. Caitlin immediately protested but Ronnie professed that they have to try and kissed her farewell, before becoming Firestorm and flying into the singularity as Caitlin watched in tears. Though Firestorm succeeds in destroying the portal Ronnie doesn't survive and is presumed killed inside the singularity, much to Caitlin's devastation.
Working at Mercury Labs
After Ronnie's death, Caitlin held herself responsible remembering Ronnie's offer to leave Central City months earlier and kept thinking what might have happened if she'd said yes but she did not blame Barry despite his assumptions.
Soon after she was employed by Dr. McGee at Mercury Labs as being at S.T.A.R. Labs reminded her too much of Ronnie, and subsequently had little to no contact with the rest of her friends. 6 months later she did however briefly attend the "Flash Day" festival. Cisco later visited her and asked her to run a DNA sample off their meta-human suspect, dubbed "Atom-Smasher" by Stein, and she reluctantly agreed. Later Barry visited her and revealed that Eobard had made a video message in the event of his death but was too afraid to watch it, so Caitlin offered to watch it with him. In the message, Eobard confesses to Nora's murder much to their shock and delight, and Caitlin decides to rejoin the team and help them defeat Atom-Smasher.
A new "ally"
After defeating him, Caitlin and Cisco see to it that S.T.A.R. Labs security is increased but as they are informing Barry of this, a stranger walks right in and introduces himself as Jay Garrick and tells them that their world is in danger. Jay reveals he knows the names of everyone present, Caitlin included, and explains that he is from another earth, Earth-Two, and more shockingly reveals he is a speedster himself named "The Flash" and was unwillingly pulled brought there as a result of the singularity as he battled another speedster named "Zoom", the same man who sent Atom-Smasher to kill Barry. Jay, however, lost his powers when he arrived and spent the last 6 months gathering information on Team Flash but a skeptical Barry asked if he'd run tests to confirm he is a speedster, which he accepted. Caitlin ran these tests and learned that Jay acquired his powers through similar circumstances to Barry, but Caitlin was quite taken to learn he was also a scientist. Caitlin learned that he did have regenerative capabilities but no evidence he has connections to the Speed Force but also ran a polygraph on him without his knowledge which came back positive. Caitlin ran further tests on him on the treadmill where she seemed to have developed an attraction to Jay, though she quickly denied it when Iris implied that Caitlin had feelings for Jay. This is further implied when Jay reveals moments later that Caitlin ran a full body scan on him at her request, and she claims she was "being thorough". Caitlin and Cisco later watched Oliver's broadcast on Star City news where he re-declared himself as the "Green Arrow", and Caitlin approved of Oliver's new name but Cisco didn't. After defeating Sand-Demon Caitlin tended to Jay's wounds and he complimented her skills and as he reflected on the loss of his powers, she also told him she'd lost something precious to her too (Ronnie) but eventually learned to live with it and they exchanged smiles. After Professor Stein confirmed the presence of multiple ruptures in the city, 52 exactly, he collapsed and Caitlin tended to him.
Seeking to use Turtle's powers to stop Zoom, Caitlin and Jay went to check on him but discovered him dead in his cell. Jay was quick to blame Harry but he denied it though Caitlin, like Jay, was unconvinced. After discovering Jay's declining health Caitlin theorizes that a fresh infusion of healthy cells could fix Jay's blood, by finding his Earth-1 doppelgänger. Caitlin asked for Barry's help but he was unable to find any Jay Garrick on Earth-1. Caitlin decided to ask Jay himself but after telling him he didn't have an Earth-1 double Jay claimed there was a good reason and asked her to meet him at Hofherr Park, where she'll see for herself. Later when Caitlin and Jay sat down at the park Jay revealed he too tried to find his Earth-1 double but with no success, at least at first. After some time, however, he eventually did find his doppelgänger and pointed him out on a bench across the park, Hunter Zolomon. Caitlin questioned why Hunter had a different name to Jay and he told her his mother died in childbirth, and after bouncing around different families was adopted by the Zolomons. However, Jay told Caitlin that his cells were mutated when he became a speedster and that Hunter's cells were no longer compatible with his as a result.
While Cisco was using his powers trying to locate Zoom he discovered that Reverse-Flash was still alive and invading Mercury Labs. However, when Barry returned from his encounter with the speedster he stated Eobard didn't know his name or that they've fought before. Harry theorized correctly that this version of Eobard is a younger version of the man they knew, one who has not yet traveled back to kill Nora and is meeting Barry for the first time. When Barry captured Eobard but wasn't allowed to talk to him because he would alter the timeline, Caitlin tried to reassure him to take comfort in the fact that he caught him. Barry, however, wasn't satisfied. When Cisco started seizing Caitlin stabilized him but he started fading out of existence to which Harry surmised was a result of Eobard's capture, rupturing the timeline, and Barry was forced to send him back.
When Barry, Cisco, and Harry went to Earth-2 to rescue Jesse, the Speed Cannon malfunctioned and Jay timely saved her from being crushed under one of its rings when it fell apart. As Caitlin and Jay tried to repair it Joe told them of a meta-human Adam Fells/Geomancer, attacking the city looking to challenge Barry. Though they didn't have Barry Joe pointed out that Jay got his speed back with Velocity-6 long enough to save Harry, but Jay refused to take it. Caitlin confronted Jay on his hesitance and he admitted that he had taken the Velocity serum prior to Caitlin perfecting it, out of selfishness for wanting to increase his speed. Caitlin then quickly realized that taking the Velocity serum was the true cause of Jay losing his speed, not Zoom, and Jay admitted he'd made so many mistakes and wasn't worthy of Caitlin's love. However, Caitlin reassured Jay she'd figure out a way to restore his speed and save him and worked on perfecting the formula, and created Velocity-7. After doing so Flash went out to stop Geomancer but during their fight, the Velocity-7 wore off, and Flash was almost killed by Geomancer but Joe was able to save him. As Caitlin tended to Jay's wounds she promised that Velocity-8 would be better, but expressed worry that Barry, Cisco, and Harry wouldn't make it back in time.
While working on Velocity-9, Caitlin discovered a flaw in its cellular matrix and visited a friend at Mercury Labs, Eliza Harmon, who helped her finish the formula, though Caitlin was careful and only gave her specific aspects so the formula couldn't be replicated in case Eliza's research was compromised. After this Caitlin was finally able to perfect the formula to Velocity-9 just in time for Geomancer to cause an earthquake that, destroyed a hospital. Before it collapsed Caitlin was forced to give Jay toe formula before testing it and Flash was able to save the people inside before it collapsed. After returning Caitlin and Iris stood in awe of Jay's achievement and Caitlin was happy to see she succeeded, and also discovered that Velocity-9's effects had begun to fix Jay's cells. As Caitlin called Jay to inform him of this however she and Iris were confronted by Geomancer in S.T.A.R. Labs and attacked them. However Caitlin was able to save Iris by using the B.O.O.T. on Geomancer, and Joe ensured Fells was arrested. When Jay did return she informed him of the Velocity-9's effects on his cells and Jay was speechless, unable to express gratitude in words so Caitlin kissed him instead. Almost immediately, however, they discovered the Speed Cannon was damaged in Geomancer's attack, but Flash and Joe were able to stabilize it. After Barry, Cisco, Harry, and Jesse returned Jay closed the last breach but before it closed for good, Zoom appeared and stabbed his arm through Jay's chest killing him and pulled him back through the portal, right in front of Caitlin. Moments after Caitlin was shell-shocked and started repeatedly saying "he's not dead" much to everyone's concern until Cisco helped her and she tried to sleep it off.
Zoom's true identity
Following Jay's death, Caitlin went into depression and tried to hide her feelings but became quite snipping and blunt, much to Cisco's concern. While the team was helping John Diggle and Lyla Michaels capture King Shark, Cisco confronted her about her cutting off her emotions but accidentally revealed he met Caitlin's Earth-2 doppelgänger. After Caitlin confronted Cisco on the subject he confirmed he had met Earth-2 Caitlin, who was a meta-human named "Killer Frost" and a murderous criminal, and Cisco expressed worry because Caitlin was starting to act just like Killer Frost with her demeanor. However, Caitlin stated that if she let herself feel the grief of losing Jay she'll never recover and she can't and insisted they get back to finding King Shark. After King Shark was captured Caitlin pranked Cisco by pretending to be Killer Frost which terrified Cisco until Caitlin started laughing. Caitlin then reassured Cisco that she may be depressed but she'll never be like Killer Frost, and watched as Barry revealed the display for Jay's helmet and vowed to find a way back to Earth-Two to beat Zoom.
While enjoying a night out at a club, Caitlin and Cisco danced while Barry, Iris, Wally, and Jesse had some drinks. Suddenly, the club was attacked by another speedster, Trajectory, who committed a robbery spree. Caitlin suspected the speedster was using Velocity-9 and told Barry about it. However, Barry was furious to learn Caitlin had the means of increase his speed the whole time, but Harry defended her as Jay had previously stated how dangerous the drug was. After Barry fought Trajectory, Caitlin suspected she may be Eliza. When she and Joe questioned her about the serum Caitlin gave her, Eliza claimed to have destroyed it after helping her, which seemingly checked out. Later at S.T.A.R. Labs, the team was attacked by Trajectory, who locked Flash in the pipeline and knocked out Joe. Trajectory revealed she was indeed Eliza, demanding more Velocity-9, ignoring Caitlin's warnings that the drug would kill her and threatening to harm Jesse. After getting more Velocity-9 Trajectory injected Jesse with a dose and escaped. Caitlin saved Jesse by giving her a transfusion of Harry's blood. After Trajectory killed herself by accidentally overdosing on Velocity-9, Barry revealed that before she evaporated her lightning turned blue, just like Zoom's. With this knowledge, Harry deduced that Zoom is dying and needs a cure which is why he wants Barry's speed, and Barry pointed out that Jay too was dying. Caitlin immediately denied the possibility that Jay was Zoom but Barry had Cisco vibe Jay's helmet, and he confirmed the revelation, much to Caitlin's shock.
After Barry and Harry created the tachyon enhancer based on Eobard's information, Barry was able to run four times faster, faster than Zoom, and realized he could take him down now. After Cisco figured out how to open breaches Barry prepared to fight him, telling Caitlin she doesn't need to partake if she doesn't want to. Caitlin, however, stood firm that she needed to help them stop Jay, whatever his real name is. When Barry questioned what she meant she revealed that Jay's doppelgänger's name was Hunter Zolomon but Harry was astounded, as Hunter Zolomon on Earth-2 is a serial killer, convicted on 23 counts of murder. After showing a newspaper of him the team realized that Jay was actually Hunter but Barry used this information to their advantage to set a trap for him. Barry successfully lured Zoom into their trap, using cutouts of the Earth-1 versions of his parents to catch him off guard, but he still escaped and abducted Wally. After agreeing to Zoom's deal to release Wally in exchange for his speed Zoom brought Wally back and unmasked in front of them, revealing his true self for the first time. While Harry prepared the device to drain Barry's speed the team questioned how Hunter was still alive, as he'd died and he revealed he'd brought a younger version of himself to the present to act as his decoy, ultimately to sacrifice him to motivate Barry into becoming faster. He also admitted he'd posed as The Flash to give people hope only to take it away from them, and Caitlin openly called him a monster. After Hunter successfully drained Barry of his speed he tried to kill him but Caitlin begged him, asking if he ever truly did care for her if he has any humanity left to let Barry goes. Reluctantly, Hunter did so, but seeing Caitlin as a weakness he couldn't let go, Hunter abducted Caitlin and took her back to his lair to Earth-Two.
While imprisoned in his lair Hunter acknowledged that Caitlin was mad at him for lying to her but told her that he loved her, much to her terror, and allowed her to roam free knowing she couldn't escape and tended to other business. While venturing she discovers a man in an iron mask using tap code against his cell, but Caitlin couldn't understand. Caitlin was then distracted by her doppelganger Killer Frost who was imprisoned in the opposite cell. Frost immediately mocked Caitlin's choice of clothing and didn't know who the iron mask was either, nor did she know why Zoom had imprisoned her. However, Frost made a deal with Caitlin that if she got her out of her cell she'd get her back to Earth-1. While working on a means to break the carbine in the cell the Caitlins talked about their very different upbringings but found common ground in their shared dislike for their mothers.
However, Caitlin Two revealed her mother was a frigid narcissist because her brother Charlie died, though Caitlin One never had a brother nor did she know why her mother was cold. After freeing Frost she immediately betrayed her and tried to kill her revealing the only reason she's still alive, is because she looks just like her, the woman Zoom loves and therefore wouldn't need her anymore. However, before Frost could kill her Zoom returned and phased through Caitlin, literally, to grab the icicle Frost made and stabbed her with it, horrifying Caitlin and leaving Frost to bleed out. Hunter then threatened to kill his masked prisoner if she tried to escape again. Later Caitlin tearfully pleaded with Hunter to let her go and Hunter agreed, as he sought to conquer Earth-1. Zoom then took him with her back to Earth-1.
Returning to Earth-1, Caitlin became a witness to Zoom's ruthless conquest of the Central City Police Department. As he killed policemen and "failed" minions without mercy, Caitlin pleaded Hunter to stop this madness. Annoyed at her demeanor, Zoom encouraged to embrace darkness instead and threatened to kill her friends next if she didn't stop meddling in his business. Eventually, Hunter presented Caitlin with a choice: stay with him, and become the queen of his meta-human empire, or leave, and share the same fate as the rest of Team Flash. As Zoom left Caitlin to address the meta-humans under his command, she escaped back to S.T.A.R. Labs Seeing her lover's merciless side took a toll on Caitlin's mental health, as she started hallucinating, seeing an apparition of Zoom appear behind her friends in S.T.A.R. Labs. Refusing to meet Hunter in person, Caitlin nevertheless agreed to act as bait for him via hologram, telling that she accepted her inner darkness, just like he wanted her to. Hunter rejected her "reconciliation" and tried to swipe at her legs, only to discover that Caitlin was but a holographic projection. He was then overtaken by Team Flash, but not before taking Joe West with him to Earth-2. After Zoom's race against Barry and his imprisonment in the Speed Force by Time Wraiths. As Barry explained how he used a time remnant to beat Zoom they awaited for Cisco and Harry to free the man in the iron mask from his predicament. Much to their shock however the man was the real Jay Garrick who was also Henry's Earth-3 counterpart. After Jay reclaimed his suit he further decided to take Hunter's helmet as a means to inspire hope whereas the helmet was meant as a symbol of false hope. Caitlin complimented Jay that it suited him. After Harry, Jesse and Jay returned to Earth-2 Caitlin attended a celebration of victory over Zoom, when Barry made a choice to alter his parents' fate, creating a "mirage" timeline known as Flashpoint.
Killer Frost arrives
Due to repressed memories of Zoom, Caitlin awakened her cryokinesis meta-human powers akin to those of her Earth-Two counterpart. She kept this a secret from the rest of the team, using them to help Barry escape Mirror Master's mirror trap. However, she later noticed while taking a shower that some of her hair turned pale blonde; she promptly cut off the altered hair to hide her powers. Desperate to understand what was happening to her, Caitlin visited her mother but was quickly annoyed when she asked if Caitlin had received her birthday card which she confirmed, in April, presumably a significant amount of time before or after it. Caitlin inquired how to get an appointment with her for a friend, not ready to reveal her secret, but as Carla coldly walked her through the procedures Caitlin angrily froze her desk and revealed she was the patient. Carla subsequently canceled all her appointments for the day and readied various tests for Caitlin. While preparing she met Carla's assistant Nigel.
Caitlin was brought down to the facility's testing lab for molecular motion where she revealed a shaft made of solid tungsten, heated to over 2000 degrees centigrade. Carla asked Caitlin to freeze it in order to determine how to reverse what's happening to her. To her horror, she froze it solidly within seconds. After Caitlin revealed the origin of her powers, she and Carla fought over Caitlin working at S.T.A.R. Labs rather than Tannhauser Industries, which Caitlin reminded her was because she desired to make a name for herself. Before they could argue further Nigel came back with the results and revealed that Caitlin had not just frozen the tungsten but had absorbed all the energy it was emitting. However, Caitlin was frustrated when she heard them talking about how her power could benefit their pursuits rather than offer sympathies. When Carla began taking blood samples Caitlin, finally having had enough, confronted her over the seemingly lack of care for her well-being and how she hasn't expressed any concern over her well being since her father died. Carla defended that she tried to save him and reminded Caitlin that she ran away but Caitlin told Carla that she had to because she wouldn't even so much as look at her. Carla accepted Caitlin's anguish and admitted that she got consumed in her work out of grief but scolded Caitlin, believing she didn't know what that kind of loss feels like. Outraged, Caitlin told Carla about Ronnie, who Carla didn't even seem to be aware of.
Having had enough, Caitlin decided to leave but Nigel trapped her in the facility wanting to exploit her powers for himself. As he grabbed her Caitlin's inner Killer Frost persona was released in a fit of pure rage and she grabbed Nigel and froze his arm solid. Carla came in to confront her, and Killer Frost ordered her mother to move, but Carla offered her apologizes, acknowledging that she wasn't much of a mother, but was steadfast that she didn't raise a killer, managing to talk her out of killing Nigel as mother and daughter hugged. Caitlin returned to help Team Flash stop the supposed monster roaming the city, only for it to be a hologram.
Caitlin later told Cisco about visiting her mother and he commended her for trying to make amends with her family. Later Carla contacted Caitlin via webcam and told her that her results proved unfruitful; that Caitlin's biology was rapidly changing and the more she used her powers the less control she'd have. After hearing this, Killer Frost's anger emerged again, as Caitlin has accidentally frozen her computer, horrified to see that she was losing control over her emotions along with her growing meta-human powers. Worried of her powers, Caitlin stole power dampeners from S.T.A.R. Labs, something that Cisco thought to blame on H.R. Wells. She was seen wearing the dampeners during an attack of the meta-human Shade. After Cisco accidentally vibed Caitlin in the guise of Killer Frost, he forced her to reveal the truth about her powers to the team.
Kidnapping Julian Albert
Caitlin said she wouldn't save Barry from Savitar, for fear of using her powers and unleashing her Killer Frost side, and only went after Iris begged her. And after using her powers to save Barry from Savitar; unfortunately, she ended up dominated by her worry and anger, turning into Killer Frost. She went after Dr. Alchemy in an attempt to rid herself of her powers. She tricked Joe into believing that Wally has emerged from his cocoon, trying to divert Joe from the interrogation of one of the acolytes of Alchemy. She tortured the acolyte, but before she could extract any useful information, Caitlin was forced to flee by approaching CCPD officers, leaving the acolyte frozen. Still obsessed with finding Alchemy, Killer Frost kidnapped Julian Albert, forcing him to create a search algorithm to find Savitar's acolytes. Julian succeeded in locating a member of Alchemy's cult, but also alerted the police to Killer Frost's location, as she tried to kill him. However, The Flash arrived and attempted to talk Caitlin down, even knocking out Albert to permit them to speak freely. Unfortunately, Caitlin was unable to control her powers; too far gone and panicked, she stabbed him in the leg and went after one of the acolytes, Craig. Upon arriving, she threatened the man's family, forcing him to comply. He informed Killer Frost that he didn't know where Alchemy was, or who he was, but only that Alchemy was merely another acolyte of Savitar who had shown them the future where, among other things, Caitlin had become Killer Frost. However, before she could press for more info on how to take away her powers, Vibe arrived and, like Barry, attempted to talk her down, but Killer Frost attacked Cisco. Barry then arrived on the scene and knocked Killer Frost to the ground.
Unwilling to surrender, Killer Frost gave Barry a kiss, using her powers to freeze him solid. Luckily, Cisco was fast enough to smite her with a Vibe burst, knocking Killer Frost unconscious. Upon waking up in the Pipeline, Killer Frost attempted to convince Team Flash she was back to normal, to no avail. She then made an offer of leaving them alone, if they release her and allow her to go on her way. But Barry refused to abandon her, angering Frost. She yelled at him, blaming Barry rightly for everything bad that happened to the team after Flashpoint. Barry returned, asking for Caitlin's help with a freed Wally West, who couldn't maintain control over his powers. Killer Frost taunted Barry, who released her on one condition: if she wanted to leave, she had to kill him. Killer Frost threatened to do so, producing an icicle but was unable to kill her friend. Crying, Caitlin finally snapped out of her anger and she hugged him, horrified at her actions. Barry comforted her and she went back with him, assisting the team in returning Wally to normal (albeit now with Super-Speed). Barry later had to make a tough choice, after Julian Albert gave him two alternatives: quit his job at Central City Police Department as a CSI agent, or he would talk to the detective outside the room. Barry decided to make a big sacrifice and quit his job to save Caitlin from a life in prison.
Fighting off an alien invasion
During a joint mission with the Legends to stop the Dominators' invasion, Caitlin mostly partnered up with Professor Martin Stein, who encouraged her to learn how to control her powers, instead of denying them, just like he did as Firestorm. On her end, Caitlin helped Professor Stein to accept his daughter, Lily Stein, who was born as a result of an accidental temporal aberration.
After the Flash has defeated Alchemy and took the Philosopher's Stone to S.T.A.R. Labs safe in its compartment box, Savitar tried to manipulate Cisco Ramon into taking the stone for himself and releasing him, appearing to Cisco in the guise of his late brother, Dante Ramon. Despite being threatened by Cisco not to approach him, Caitlin managed to talk him down and persuade to hide the Brahmastra, stopping Savitar again. Later on, Caitlin was present when Team Flash communicated with Savitar, possessing the body of Julian Albert. She was worried as he claimed a prophecy for Team Flash, saying that one of them would fall, the other betray them, and the other would suffer a fate worse than death. After this ordeal, Caitlin encouraged Julian to come to celebrate Christmas together with Team Flash at West house, later on congratulating the CSI specialist when he came to the party after all. Showing Cisco that she took Martin Stein's advice to heart and started to practice control over her powers, Caitlin removed her power dampener and produced an icy mist with her hand, turning a rain cloud above the West house into a cloud producing snow.
A mysterious future villain of the Flash named Abra Kadabra appeared, stealing from several tech companies in an attempt to build a timeship to return to the 64th century. Abra Kadabra soon found himself chased after by the Flash and Gypsy, escaping, but not before telling Flash that he knew Savitar's name.
Sometime later, he teleported into S.T.A.R Labs and ambushed Caitlin, Julian, and Joe West, but was soon apprehended by the Flash and locked up in the Pipeline, taunting the team about his knowledge of Savitar. There, he told Joe that if he let him escape from Gypsy, he promised to reveal Savitar's name so the team could save Iris. Joe agreed and set him free, but Kadabra betrayed him, claiming that the terms of the agreement had changed. He then went to collect a mysterious future power source from the Time Vault and set off an explosive as the trio attempted to chase after him upon his escape. The resulting explosion impaled Caitlin's side with shrapnel. Team Flash took her to the med bay and helped her onto the bed. Caitlin showed signs of physical pain, as she was breathing heavily and moaning. Cisco tried to stop the bleeding with a T-shirt while the team decided how they were going to help her. Julian X-rayed her and found she had bits of metal wedged inside her that needed to come out. Caitlin refused to go to the hospital as they will find out about her Killer Frost identity. Iris told the team that Caitlin couldn't operate on herself but Caitlin said she could if she had a mirror, she could talk someone through the surgery.
Soon after Caitlin talked Julian though her own surgery. Iris helped stop the bleeding as Julian operated. As Julian came to the last piece of metal he found that it was stuck, as he tried to get it out, Caitlin's heart rate began to increase dangerously, causing Cisco to worry. Julian told her it was going to hurt as he pulled the metal out, Caitlin screamed in severe pain before becoming light-headed and telling Julian to stitch her up as she was going to pass out. Not too long after she woke up in the med bay bed with Julian holding her hand. Julian told her how brave he thought she was before getting up to kiss her, but pausing out of fear of hurting her. Later that day, Cisco was alone with Caitlin.
She seemed to be recovering well, but as they were talking, Caitlin stopped mid-sentence and passed out. She then started seizing. Cisco panicked and called for help. Julian came running in with H.R. and they tried to hold her down, but she suddenly stopped moving, with the monitor recording her heartbeat flat-lining. Cisco put his hand above Caitlin's mouth and found that she wasn't breathing. Julian began giving her chest compressions and told Cisco to get the oxygen mask and place it over her mouth. They then tried the electric shock, but everything was unsuccessful. Julian tried more compressions while Cisco continued giving her oxygen but Caitlin wasn't responding and they couldn't resuscitate her. Cisco started crying, realizing his best friend had died. Julian, distraught, ripped off Caitlin's necklace, hoping her meta-human powers could regenerate her. About 30 seconds later, she began breathing again. Caitlin's wound also healed instantly, but she emanated a cloud of mist, sending the team and herself flying. Once the cloud cleared, Caitlin had transformed into Killer Frost and attacked the team before escaping.
Caitlin wandered around in the snow, only to encounter Savitar. She asked if Savitar wanted to cure her, to bring Caitlin Snow back, but the armored villain wanted just the opposite. Caitlin then asked Savitar why should she trust him. To prove that he can be trusted, Savitar removed his armor and revealed himself as a future version of Barry. Seeing who it was, Caitlin agreed to do anything he wants.
Hunting Tracy Brand
She was sent by Savitar to the Central City University in order to kill future physicist Tracy Brand, however, her attempt on the scientist's life was thwarted by the intervention of Barry and Cisco. She returned to Savitar to tell him of her failure. Savitar questioned Frost's loyalty by pondering the idea that there may be more Caitlin Snow still within her than she led him to believe, especially due to the fact that despite taking up the name Killer Frost she had not yet actually killed anyone. He then told her to once again try to kill Tracy with the promise that if she succeeded they could both be gods.
A few hours later she kidnapped Cecile at the West house and told Joe that the only way to spare Cecile's life would be to trade her for Tracy. At the site of the trade-off, she battled both Barry and Cisco before being overcome by Cisco's powers and knocked unconscious. Cisco then acquired a blood sample from her that Julian hoped could be key, due to Caitlin undergoing a full mutation into Killer Frost, to reversing the process and cure their friend. Before the team could return to S.T.A.R. Labs, to presumably lock Frost away in the Pipeline for their and her own safety, Savitar appeared and escaped with the still unconscious Killer Frost.
When Savitar lost his memory, Killer Frost realized that Team Flash erased Barry's memory to prevent the future Savitar is trying to create; but this also caused Wally to lose his powers. She offered them the hard choice of returning Barry's memory or leaving Central City vulnerable to attacks by meta-human criminals. Cisco encouraged her to remember being Caitlin Snow, which allowed her to help restore Barry's memory in surgery. She prepared to leave, with Julian confessing that he had fallen in love with her. This news briefly shocked Killer Frost, who coldly told Julian that she never loved him, then saying that went for the entire team. When in the elevator, her eyes briefly returned to normal, showing that Killer Frost could be turned back into Caitlin.
In a news report on a television reporting the arrest of Jared Morillo that Barry saw during his accidental trip to May 2017, a subheading read "Killer Frost still at large". While Barry succeeded in altering the circumstances of Morillo's arrest, with Wally defeating him instead of Barry in January instead, Caitlin's future remained the same. Barry later reveals to Joe that Caitlin's on the loose and they need to bring her in, prompting him to alert the CCPD. This causes the aforementioned headline.
Killer Frost was later seen talking to Savitar about his plans if he's really ready to end his former lover's life. He then stated that "It's either her or me", and that when the time comes she should be ready to do her part. When Savitar captured Iris HR Wells risked his life to stop him he switched appearances with her, so when Frost attacked them she didn't realize that she was actually taking back HR. Caitlin then met Vibe in a snowy forest area and said that she needs to "cure herself of Caitlin" and the only way to do that is to kill him. As the fight went on Killer Frost gained the upper hand. Right before Frost could finish off Cisco, Savitar appeared and stated she should keep him alive, as he needs him to modify the Speed Force Weapon. Later on, after Vibe finished making the modifications, Savitar ordered Caitlin to kill Cisco, which she tried to do, but Gypsy interfered and the two escaped.
Killer Frost then helped Savitar get rid of the Black Flash, and then used the weapon on the God of Speed. While interrupted by Team Flash, she took on Gypsy and Vibe but was subdued. Cisco then offered Killer Frost the choice to use the cure and become Caitlin again or remain in her current state. When Savitar attacked Cisco and attempted to kill him, Killer Frost, without using the cure, managed to take control of herself and let go of the mad persona. She attacked Savitar and watched his defeat by Barry. Caitlin later attended the funeral of HR Wells, where she met Julian and Cisco. She told them about her decision to leave, in the hope that she can rediscover herself. Caitlin and Team Flash bid each other goodbye and she departed on good terms.
Rediscovery and return
Working for Amunet Black
Trying to find her own way in life, Caitlin left S.T.A.R. Labs and journeyed away. Struggling to cope with Killer Frost, Caitlin took Julian's serum, but this only suppressed her temporarily and her alternate personality soon resurfaced, stronger than before. Afterward, Caitlin was contacted by Matthew Norvock, a member of Amunet Black's organization, and worked for them as Amunet's henchwoman. In exchange, Amunet used a transmodular genetic splicer, a piece of black-market technology, to apparently split Caitlin and Killer Frost. During this period, Caitlin kept a low profile and didn't use her credentials to get a prominent job, instead of becoming a bartender.
Rejoining the team
During Samuroid's attack on Central City Cisco vibed Caitlin's location and visited the bar she worked in. He managed to convince her to return to the team, where she helped Cisco in locating and later diagnosing Barry, much to Iris's hatred. Rejoining the team, Caitlin worked on helping to get Barry back to sanity, including using the speedster weapon to stop his mad rampage. Reuniting with Barry, apologizing before Joe and trading banter with Cisco, - all of it influenced Caitlin into leaving her job and coming back to S.T.A.R. Labs. She informed her associates at the bar about her decision to leave and was confronted by Norvock, who tried to strong-arm Caitlin into staying, threatening her for not listening to Amunet's orders. Angered by such an attack, Killer Frost used her meta-human powers to intimidate Norvok, nearly killing him via brain freeze and saying "Touch my hand again and I'll freeze yours off. Maybe some other parts too." Afterward, Killer Frost was riled up enough to go "have some fun" on a rampage but Caitlin managed to force herself out of the violent mood, restoring her hair and eyes back to their natural color.
After Cisco finished running Barry through all the new functions of his suit, Caitlin overheard his conversation with Iris and took the opportunity to suggest couples counseling to her which she harshly and rudely declined stating that they would be fine since they're "Barry and Iris" (like that means anything). After their talk, the alarm for an unauthorized breach went off and Iris shouted to Caitlin to come with her and apprehend whoever it was, however, Caitlin turned her back as her eyes began to glow white, signaling Killer Frost attempting to take control. After Iris called her name a final time, her eyes returned to the normal brown and she followed Iris to the speed lab. When they got there, they were aiming weapons at the breach when Wally sped in, they all prepared for an attack until Cisco ran in and told them all to stand down. After many confused glances were sent his way, Gypsy ended up coming through and the three calmed down and exited the lab.
After Barry saves Tim Kwon, whose car had apparently been hacked, the team take the parts of his destroyed car and plug them into a computer only to find that it had the same code as the elevator that killed Kurt Weaver. Caitlin then recognized the code and revealed that it was an organic virus with a digital sub base. Cisco then recognized the names of the victims and him and Caitlin went to start digging into their past.
Caitlin and Cisco were working on finding out how the victims were connected in his lab until Gypsy walked through the door, wondering when she and Cisco were going to go on their date. Cisco then said that he found a picture that could help them in the mystery but couldn't identify one of the people in it. After Barry then saves Joe from a rogue bomb robot in CCPD, the team discovered that the man in the photo was Ramsey Deacon and he had the ability to control any form of technology. Caitlin and Cisco, still in his lab, were still looking for a weakness in Deacon's powers when Gypsy walks in, still wanting to know about her and Cisco's date. He then is forced to cancel their date and Gypsy just lets him know it's fine. While Cisco thinks she is really is okay, Caitlin tells him that it meant she was not okay, he explains that he doesn't get it and she pats him on the back and leaves with a smile on her face after telling him, "You, my friend, are in SO much trouble".
Later, after Deacon attacked Sheila Agnani and kidnapped Tim Kwan, Joe, Wally, and Caitlin were looking for both Deacon and Kwan using facial recognition and traffic cams, but to no avail. Iris then asks Cisco, who storms off after thinking about Gypsy, Caitin then goes to talk to him. After trying to calm him down, Gypsy jumps into his lab through a breach and explains that she is fine with him canceling their date but Cisco remembers everything Caitlin told him and says that when a woman says it's fine, it's not actually fine causing Caitlin to get excited and shout "Amen!". Getting stares from both Cisco and Gypsy, she leaves the room, embarrassed. Later, the team go to the cortex and see a broadcast of Kwan explaining that he and his friends stole the Killg%re project from Deacon. Before Barry goes to defeat Deacon, Caitlin gives him the serum her and Cisco created in order to beat him. After getting his suit hacked and almost being killed, Barry is able to defeat Deacon and he gets incarcerated in Iron Heights.
After the pipes in the West house were making strange sounds, Team Flash spent a day out together where they played a game of laser tag together. After the game, they sat and had lunch just before the breach alert went off and they rushed back to S.T.A.R. Labs. When they reach the building, they find Wally and Harry in the breach room. Harry gives Wally a break-up cube with a message inside from Jesse who wanted to break up him after becoming so busy on Earth-2. After this an alarm goes off, signaling a problem a bank in the city. Before they leave Caitlin angrily tells Harry that they're not done. After Barry fails to stop the newest meta-human threat, Becky Sharpe, Cisco, Caitlin, Harry, and Barry all watch the footage in the cortex until Joe and Iris walk in and are able to identify Becky. They come to the conclusion that she is a meta-human with the ability to manipulate luck but don't know how she could have powers since she wasn't in Central City when the particle accelerator exploded. They all begin working in their respective jobs to understand where she obtained her powers.
Later, Barry, Cisco, and Harry come back from looking where Becky got her powers and reveal that Barry coming out of the speed force caused people to become meta-humans. When looking for a plan, Cisco and Harry start to fight and Caitlin attempts to calm Cisco down but he simply states that they don't need him to beat Becky. Barry later tried to talk to her face to face but to no avail as she just caused more people to almost getting hurt. He then returned to S.T.A.R. Labs and attempted to come up with a plan with Cisco, Caitlin, Wally, and Joe where Cisco ends up naming Becky "Hazard". The rest of the team felt like they had been jinxed and Barry had to talk some sense into them until he gets a call from Iris and leaves. When an alarm sounded in the cortex, everyone ran in and Caitlin explained that there were events caused by bad luck all over the city, which meant that Becky's field of bad luck was growing, they all come to the conclusion that the more good luck she experiences the more her field would grow and the more people suffer. To make matters worse, Becky's field caused the particle accelerator to turn back on. Luckily, Becky ends up suffering bad luck when she didn't win in a casino which caused her field to shrink and Barry managed to get the power-dampening cuffs on her, meanwhile, Cisco and Harry were able to deactivate the accelerator. After everything calmed down, the team managed to figure out that when Barry came out of the speed force, he affected everyone on Central City Bus 405 and gave them all meta-human abilities. After this, Wally also ends up leaving the team due to his break up with Jesse. Caitlin gives him a hug and tells him "good luck".
After roaming the corridors of S.T.A.R. Labs, Caitlin comes across Breacher and when she reaches the cortex she asks Barry and Joe "why is the scariest person I have ever seen roaming our halls?" and they only respond with "Cisco". They then pull up a photo of Ralph Dibny and explain that he was a former corrupt cop that could've been on the bus on the day of Barry escaping the Speed Force. As Barry leaves, Caitlin and Iris comment on Ralph's handsomeness, comparing him to Oliver Queen. After Joe and Barry pay Dibny a visit, they discover that he is indeed a meta-human from the bus and take him back to S.T.A.R. Labs. When Ralph gets there, his legs are stretched out so far that his foot is in the hallway, and as Barry and Caitlin attempt to calm him down, Iris runs in screaming in terror. While attempting to figure out how his powers work, both Harry and Caitlin refer to him as "Silly putty", visibly upsetting him. They all then get into a fight that Caitlin quickly stops when she explains that she needs a sample of Ralph's blood and his arm elasticates, tripping her and making her accidentally throw powder in Ralph's face, causing him to sneeze and his face to fall into his hands, causing Joe to puke.
After calming Ralph down, the team returns to the cortex, and Iris asks Caitlin if there is anything she could do to help Ralph. She then explains that she would need a DNA sample of Ralph's before he was exposed to dark matter. However, Barry asks why she would help him considering he was a corrupt cop and is still a bad man, and Caitlin explained that she took an oath and had to help him. When he refuses to consider that Ralph has changed, Caitlin brings up past events of her becoming Killer Frost. Barry then reluctantly goes to Ralph's office in order to find a sample. He later returns with Ralph's hairbrush, having narrowly escaped a bomb someone had planted in the office. When Barry begins to make remarks about Caitlin becoming buddies with Ralph she explodes with rage on Barry and explains that she understands what it's like to wake up one day with strange powers, which causes Iris to look at them and realize they are arguing like they are a married couple. The two are then interrupted by Joe entering the room but still shoot each other angry glares. Later, Caitlin manages to complete a serum that would help return Ralph to normal and gives it to him. When he drinks it, his limbs return to normal and she explains that he can be any shape he wants to be. He then reaches down to his stomach and reduces his fat into abs.
After Caitlin runs some test on Ralph, Barry and Joe enter the cortex and exclaim that they know Ralph is threatening the mayor with the information that he is cheating on his wife. When Ralph attempts to leave, Barry grabs him and the two begin to fight but when Barry goes in for a punch, his fist goes into Ralph's face. Angry, Ralph leaves the lab, leaving Team Flash shocked. Barry later stops the corrupt Mayor Bellows and reveals his identity to Ralph. The two then return to S.T.A.R. Labs and Barry and Joe reveal to Iris and Caitlin that Cecile is pregnant and all four of them embrace. Later, Caitlin returns to apartment to find a message written on her door by Amunet Black, saying that she misses Caitlin.
Embracing Killer Frost
After receiving the message from Amunet, Caitlin books a flight in order to get out of Central City. Just as she is confirming it on her computer, Iris and Felicity walk in and push Caitlin into attending Iris's bachelorette party. She ultimately agrees but worries that Amunet may find her. Caitlin, Iris, Felicity and Cecile attend the party at a fancy restaurant and Iris notices that Caitlin is drinking excessively. When she looks to the entrance, she witnesses Norvok enter and walk to the girls' table. He asks her to come with him and Felicity mistakens him for a male stripper and when she asks him to take his pants off, he takes out his eye instead. Caitlin flips the table and Iris and Felicity begin attacking Norvok but are ultimately thrown to the ground. When he looks to Caitlin, Killer Frost takes control and the girls are shocked as they watch Caitlin's transformation. Frost then shoots a beam of ice at Norvok, knocking him out of a window and remarking "Ugh! I hate pink" then taking a big sip of the champagne. The three return to S.T.A.R. Labs and Killer Frost retrieves her suit that was stashed hidden from everyone. She then leaves the three other women at the lab and travels to Amunet's nightclub to confront her.
Once she arrives, Amunet is pleased to see her and shows her a meta-human that she has been keeping hostage in order to harvest his powers and sell them as a drug. She then proposes that she and Frost work together to take over the city and become Gods, however, Frost denies this offer and Amunet grows angry and begins to use her powers to slowly raise her metal in a bag beside her. Just as Frost raises her hand, ready to shoot an ice beam, Iris interrupts the two of them and compliments Amunet on her club and then asks Frost to come with her to get out of the club. After considering it, Frost complies and follows Iris out. When they return to the lab, Frost begins to get her things together and tells the girls about Amunet and her history with Caitlin. Just as she is about to leave, Iris manages to convince Frost to stay and fight Amunet instead of run from her. She leaves the lab and meets her under a bridge somewhere in the city and the two begin to fight. Killer Frost shoots at her with two ice beams but Amunet creates a metal shield that deflects both and then launches a large piece of metal into Frost's shoulder. Amunet then picks her up and begins to punch her several times, causing Frost to retreat back into Caitlin's mind and letting Caitlin take all the punches. Two officers pull up next to the scene, which distracts Amunet long enough for Caitlin to escape.
Back in the lab, Caitlin, now back in control, treats her own wounds and is finishing up as Iris walks in to check up on her. She helps Caitlin finish the last stitch on her shoulder and she asks Iris if Killer Frost had hurt anybody. When Iris explained that she didn't, Caitlin regretted coming back to the team and told Iris that she didn't consider her a real friend, only a "work friend" later stating as Killer frost "if you still wanna have a hand for Barry to put a ring on, I suggest you move it". Later, the girls get a location on Amunet and go to confront without Caitlin. However, the plan goes south and she catches Felicity and Iris but before she can kill them Caitlin enters and tries to make a deal with Amunet in exchange for her friend's lives. Her men then point their guns at Caitlin but she screams and sends an ice blast from her mouth at them, knocking them all down and bringing out Killer Frost. The girls get behind her and she creates an igloo around them to take over from Amunet's metal shards. They get the idea to use a magnet to stop Amunet using her powers and Frost explodes her igloo, knocking out all of Amunet's men. As Amunet gets ready to shoot her shards at the three women, Cecile turns the giant magnet on which attracts all of Amunet's shards. Killer Frost then forms an icicle in her hands and prepares to stab her before Iris foolishly stops her and tells her she can choose to be a hero. This gets through to Frost and she drops the icicle but Amunet promises to get her back and escapes, all thanks to Iris. Back at the lab, the boys return from the bachelor party and see Killer Frost standing in the cortex. She transforms back into Caitlin and explains everything about Frost. Later, Caitlin and Iris leave together and Iris asks her to be her maid of honor, which she accepts.
After this, Caitlin accepts Killer Frost as a part of her and the two begin working together as a team.
After Ralph told the team that he received an anonymous tip from some named "DeVoe", Caitlin, Cisco and Harry stayed up all night researching the entire city in order to locate someone with the name. Harry then reveals that he had met new friends who could help them with locating the mysterious "DeVoe". While Harry was contacting them, Barry recommended that they search for the remaining bus meta-humans and asked Ralph to try and identify some of them since he was on the bus. After visiting Dr. Sharon Finkel, Ralph was able to remember a woman wearing a yellow jacket with a bison on the back. A crime scene later showed up and Barry found blood on a statue, causing him to think that the statue may have came to life and so he brought a piece of it to Caitlin. She explains that the statue was flooded with dark matter and it was most likely a bus-meta. Joe then enters the cortex and explains that the victim of the crime scene was transporting an artifact that was formerly in the possession of Kristoff Banks and he then went back to CCPD to put Banks into protective custody.
After Banks is almost killed, the team identify the meta as Mina Chaytan. After Chaytan attacks a truck, Barry and Ralph are able to stop her and successfully incarcerate her but she is later able to escape custody and make her way out of CCPD. She then attacks a museum in order to steal back more ancient artifacts but is stopped by Barry and Ralph and incarcerated again, for good. Later, the team are able to identify and track down the mysterious DeVoe and Caitlin, Cisco and Ralph suit up as Barry and Joe walk up to his home in their civilian attires but when they knock on the door, a wheelchair-bound Clifford DeVoe and his wife, Marlize, answer the door, appearing to be quite normal people.
After Barry and Joe interview DeVoe and his wife, they return to the lab and the team debate whether or not he is the DeVoe they are looking for with Barry assuring everyone that he is the villain. He later manages to steal DeVoe's mug of coffee in order to get DNA for Caitlin to identify him as a meta but she is able to confirm that he is not a meta-human. However, Barry is still convinced that Clifford was the criminal mastermind behind the bus metas, even getting Cisco to vibe his mug but only seeing that he was having dinner with his wife. While the team were sitting in the cortex, Barry walks in and shows them that the samuroid head had a camera in it and is convinced that it is DeVoe watching them. However, they find out he broke into the DeVoe house and believe that Barry has become obsessed with him. Later, Barry reveals that DeVoe knows he's The Flash and that he was right about DeVoe being evil, convincing the team that he needed to be stopped. Cisco even comes up with the name "The Thinker". After the explanation, Wally walks into the cortex and everyone runs to hug him. The team then explain that they are going to wait for him to make a move and get ready for Barry and Iris's wedding.
Crisis on Earth-X
Before the wedding, Caitlin, Iris, Felicity and Kara Danvers went together for a manicure and discussed Felicity's relationship with Oliver and his son William. Caitlin remarked that they would be getting married too any day soon and the girls toasted to Barry and Iris. Later that night, before the rehearsal dinner, Caitlin encountered Martin Stein and the two sat down to speak. He commented that the last wedding they both attended together was Caitlin's and even mentioned Ronnie. Caitlin also told him that she helped Cisco and Harry create a serum to separate him and Jax and he told her that he knew since he saw her brilliance in it. She then left to go to the dinner and Martin told her he'd be there soon. At the rehearsal dinner, Caitlin ran into Mick Rory, who had previously kidnapped her back when he was a criminal, and she warned him no to try it again. The next day, the wedding ceremony was attacked by Nazis from Earth-X and the priest was killed by them. During the chaos, Cisco recommended Caitlin introduce Killer Frost, causing her to surface and join in the battle. Frost rose and began firing shots of ice at them, gaining the attention of Mick Rory who helped her. She then created a giant icicle over her hand and stabbed a series of Nazis. After the battle, the heroes return to S.T.A.R. Labs and Caitlin and Martin watched over Cisco who had been incapacitated. When Martin asked why Caitlin was dressed in her suit, she explained how her and her split personality work, which astonished him.
After discovering the Prometheus of Earth-X is Tommy Merlyn's doppelganger, the heroes came together in the Cortex and Harry explained the history of Earth-X, telling them about the Nazis winning WWII and Hitler's only dying in the 1990s. After the meeting, Caitlin and Harry worked together using dimensional vibrations to find the Earth-X Nazis. Caitlin, Harry and Jax attempted to work in Cisco's workshop but knew that dimensional breaching was Cisco's speciality and since he was incapacitated they couldn't find the Nazis. Martin then entered the lab and requested Harry and Caitlin leave so that he could talk to Jax alone, concerning their identity as Firestorm. The team later discovered that Dark Arrow and Overgirl were the doppelgangers of Green Arrow and Supergirl and that the Nazi speedster was Eobard Thawne who had somehow returned again.
Later, Caitlin, Harry and Felicity were attempting to find the Nazis when Caitlin was approached by Mick who asked how she brought Killer Frost to the surface. She explained that Frost appeared whenever she was scared or angry. Mick then humorously shouted "boo" in an attempt to scare Killer Frost out of Caitlin but he was only given an angry glance by everyone in the room. During this, Harry found out how to track down Overgirl and that they should be able to track down her location any minute. After they find the location, Green Arrow, White Canary, Supergirl, Alex, Firestorm and The Flash all go to apprehend the Nazis. However, this turned out to be a distraction to the lure out the heroes so the Nazis could take control of S.T.A.R. Labs. After handing Mick the German Mustard he was craving, Caitlin, Felicity and Iris all hear an alarm go off to alert them of Dark Arrow's arrival. The four went to the Speed lab to hide from him and when he arrived, Mick attacked him head on but Killer Frost came up from behind and managed to grab his bow, beginning to freeze it. However, it sent out a wave of energy that knocked her back against a wall. Black Canary, Wild Dog and Mr. Terrific then began to attack. This was all in vain as all the heroes were locked in the pipeline by the Nazis.
When stuck in the pipeline, Cisco finally woke up and immediately began to argue with Harry. Caitlin gave them a quick warning to stop but they continued anyway. Dinah, annoyed, then asked Caitlin if they were going to be like that the whole time they were trapped and Caitlin replied with a simple "probably".
The rest of the Legends eventually arrived at S.T.A.R. Labs and rescued the heroes trapped in the pipeline. As they entered the speed lab, the group was ambushed by Metallo. However, he was no match for them as Caitlin turned into Killer Frost and all of the combined abilities of Frost, Vibe, Black Canary, Wild Dog, Firestorm, The Ray, Heatwave, Zari Tomaz, Vixen and Steel come together and completely destroy Metallo. During the battle on Earth-X, Stein was injured so Caitlin, Jax and Martin rushed to the med bay on the Waveriderin an attempt to save him. Caitlin quickly ordered Gideon to stop his bleeding and after she did, Jax suffered a fit and went into the same state as Martin due to them being linked by the Firestorm Matrix. Caitlin suggested that they merge as Jax is the only thing keeping Martin alive. After Caitlin did everything she could, Jax woke up and asked about Martin and Caitlin explained that he was sedated and that she and Gideon were doing everything they could to fix him.
Knowing that Martin's fate was likely sealed, Caitlin left the room and went to talk to Ray. She explained the situation and that Jax was acting as a human life support machine, keeping Stein alive for only so long. Ray remained optimistic that someone on the ship could figure something out. Jax later accepted this and was asked by Martin himself to end it, which he did, killing Martin. Caitlin and Cisco both stared out of the main window of the Waverider as they both mourned Martin's death. Later, Oliver gave a speech about never giving up and stated that they could beat the Nazis, which Killer Frost complimented. Gideon then informed everyone that the Nazis were attempting to contact the heroes. They all stood together as they spoke with Dark Arrow and he demanded Supergirl come with him and they would return to Earth-X quietly. Oliver refused, declaring war and the heroes went out on the battlefield. In order to destroy the Earth-X Waverider, the heroes needed someone on board to self destruct it manually. To do so, Killer Frost, Vixen and Zari all managed to get on board using Frost's ice path. The three managed to self-destruct the ship and escaped through a breach created by Cisco. In the end, the heroes managed to defeat the Nazis and everyone attended Martin's funeral. As Caitlin dropped dirt on his coffin, she asked him to tell Ronnie that she misses him.
Kidnapped by Amunet
During the holidays, Cisco decorated the Cortex with a huge blue Christmas tree and as him and Harry began arguing about the tinsel, Caitlin entered and asked where Gypsie was. He explained that she had to work on the holidays and couldn't make it to Earth-1. When Ralph entered, he mentioned an inside joke he had with Cisco, Harry and Killer Frost, leading Caitlin to believe that her friends would much rather hang out with Frost than with her. She then left to get a coffee at Jitters. At Jitters, Caitlin had a Killer Frost drink as Harry approached her. He told her that even though Ralph may have said that Frost was more fun than Caitlin, Harry thought that she was special and that her friends would much rather hang out with her than Frost. Just as the conversation ended, Amunet burst through the glass doors of Jitters and called out for Caitlin. Harry attempted to hold her off with a gun but she quickly disarmed him and smashed the gun, when she found Caitlin, she tried to turn into Killer Frost but Amunet swiftly grabbed her and put power-dampening cuffs on her.
Amunet took Caitlin to an abandoned hospital building an showed her an injured meta-human she had "found". She explained that she was planning on selling him but he wouldn't come quietly so she was forced to shoot him which ended up with him having a metal shard stuck in the side of his head, ultimately forcing her to seek out Caitlin to help him. Caitlin quickly accepted and explained that she would do what she could considering she wasn't in an ideal environment. When the meta-human woke up, Caitlin introduced herself and he also did, introducing himself as Dominic Lanse. While explaining their situation, Caitlin discovered that he had the ability to read people's minds. Later, when preparing for the surgery, Dominic read Caitlin's mind and asked her about who Killer Frost was, forcing her to explain her alternate personality and how she works. She then questioned if they would ever escape due to her not having her powers at the time, but allowing her to realise that Dominic had powers that could help them.
The two snuck out of the hospital room and used Dominic's telepathy to spot any thugs around corners. However, this quickly failed as they were eventually cornered by Amunet and her men who brought them back to the hospital room. On the way back, Amunet questioned why Caitlin attempted to escape when she hasn't been injured once by Amunet the whole time and Caitlin revealed it was because she was doubting herself. Amunet then revealed that she was once a stewardess, who was constantly hit on by perverted pilots until she obtained her powers and made them pay. She told Caitlin that she was the brightest woman she knew and that she was capable of completing the surgery no matter the circumstances. She then ordered her to get back into the hospital room and complete the surgery.
During the surgery, Caitlin successfully removed the shard of metal and began to stitch Dominic up until he began to go into shock, causing Amunet to move her bag of metal shards, threatening to kill Caitlin. However, it was then revealed that Caitlin and Dominic had devised a plan to escape and managed to lace the ventilation with anaesthetic, knocking out Amunet and her men. The two ran out of the hospital but Amunet managed to catch up to them, almost stabbing them both in the back of their heads. They were almost shot again until Ralph and Cisco arrived and stopped the shards from hitting them, Cisco knocking back Amunet with a vibe blast. The four then escaped through a breach created by Cisco. The next day at S.T.A.R. Labs, the team discuss where DeVoe could be and that he could've potentially drowned after being thrown into water by Barry. That night, they have their annual Christmas party at the West house with even Dominic showing up. However, it is revealed to only Barry that Dominic was actually captured by Amunet and sold to the DeVoes, who killed him and allowed DeVoe to stab his own body and take over Dominic's. DeVoe's body is later left at Barry and Iris' apartment with a knife in his chest, framing Barry for his murder and getting him arrested by the CCPD.
After Barry was questioned by the CCPD, he was placed on house arrest but was able to attend a meeting in the cortex by Cisco hacking into his ankle monitor. After discussing DeVoe's plan, Barry agreed to go to Iron Heights if he was convicted, not wanting to become a fugitive. The whole team attended Barry's trial at the courthouse and after the lawyer mentioned the knife that was used to stab DeVoe, Caitlin noticed Iris was visibly upset and grabbed her hand. However, Joe got a message about a meta-human attack in the city, forcing him, Caitlin and Cisco to leave Iris with Barry in the courtroom. After studying the medical records of the victims that passed out at Central City Bank at the hospital, Caitlin entered the cortex and explained everything to Cisco and Harry. She told them that they had all suffered from radiation poisoning and that they needed to find the meta-human before he poisoned the whole city or even worse, became a nuclear bomb. Cisco even nicknamed the meta "Fallout".
Later, Cisco and Harry managed to get a location on Fallout and the two went to try and apprehend him while Caitlin stayed and monitored them from the cortex. However, this only turned out to be a waste disposal truck. They finally managed to get a correct location on Fallout and called Barry, forcing him to postpone his conviction. Harry and Cisco then concluded that they needed Killer Frost in order to cool Fallout down and stop the nuclear explosion. At first, Caitlin can't transform because she needed to be scared or angry but after Cisco began listing things that would be destroyed if she didn't fight, Frost finally emerged. After jumping through a breach, Cisco and Killer Frost reached the location and Frost immediately froze Fallout with an ice blast. However, he managed to thaw his way out and shot a beam of radiation at her, sending her flying through a bus sop and knocking her unconscious. Barry and Cisco eventually managed to defeat Fallout and he was incarcerated at A.R.G.U.S.. However, Barry is later convicted and sent to Iron Heights.
Losing Killer Frost
After assaulting S.T.A.R. Labs, killing Matthew, Janet and Edwin; taking their skills and possessing Ralph Dibny, Clifford DeVoe had a confrontation with Vibe, Killer Frost and Flash. When Killer Frost grabbed him to stab him with a block of ice, he used Brainstorms powers to create a psychic block on Killer frost, thereby taking Killer Frost out of Caitlin but not completely taking her from existence.
Caitlin was saddened because she was starting to come to terms, and form a kind of friendship with her other personality. She subsequently tried everything she could think of to try to get her alter-ego back. She concluded that it was possible to get Killer Frost back, she just had to find a way to make her appear.
Trying to recover Killer Frost
The team began to help Caitlin to try and get Killer Frost to reemerge, they ran tests that involved Cisco shooting her with his vibe blasts, which caused nothing to happen. However, while Barry and Cisco are fighting DeVoe, Caitlin appeared and used Leonard Snart's gun on DeVoe in an attempt to get Killer Frost to return, but to no avail as he almost killed Gypsy.
Still desperate to get Killer Frost back, Caitlin finally went to Amunet for help. She led the team to believe that they needed Amunet to help defeat DeVoe and they all managed to get her to help them. Caitlin then struck a deal with her and told her that if she could get Killer Frost back she would do one favor for her. However, it's revealed that Amunet didn't know how to bring her back but still gave Team Flash an item that could help defeat DeVoe.
When Caitlin went to therapy with Dr. Sharon Finkel, she revealed that Caitlin had been repressing a memory from her childhood, a memory which was very traumatic for her. She later asked Cisco to vibe her to this memory and see what happened only to see her younger self get hit by a car and then transform into Killer Frost. This revealed that Frost had been inside Caitlin even in her early childhood, before the particle accelerator explosion.
In the final battle against DeVoe, when Cecile went into labor, her powers which she received from her pregnancy kicked in and Killer Frost briefly inhabited her body. She grabbed Caitlin's arm and told her that she had found Thomas and he had been that way all the time.
Searching for her father and recovering Killer Frost
Team Flash had discovered that Caitlin's father's death certificate was a fake and that he was actually alive. Barry, Caitlin and Cisco eventually tracked him down to a warehouse owned by Tannhauser Industries. However, it was later discovered that he was also a cryogenic meta-human that had an evil split personality that attacked the team. The personality wanted to use a serum, that Caitlin reluctantly created, to kill off Thomas for good and inhabit the body himself. Just as he was about to inject himself, Caitlin managed to break through the mental block that DeVoe had created, allowing Killer Frost to emerge and shoot him back with an ice blast. He quickly attempted to convince Frost to take the serum as well and work with him but she refused, stating that Team Flash was her true family. As she walked towards him, she stood on and destroyed the serum. She created an ice-fist and began to punch him but stopped as Thomas' personality emerged and spoke to Caitlin. This turned out to be a short reunion as the evil personality reemerged and shot her back with an ice blast, proceeding to use two ice blasts to launch himself into the air and escape. Later, Caitlin discovered that she could use the cerebral inhibitor to speak to Frost through the mental block and the two began to catch each other up.
During Thanksgiving, Caitlin, Cisco and Sherloque decided not to attend the party at Barry and Iris' apartment, causing Killer Frost to emerge. She questioned they're decision of eating by themselves instead with friends who care about them and proceeded to walk off to the party, asking if they were coming or not.
During a battle with Cicada, the entire team was taken down by him, noticing this Caitlin and Sherloque were running ready to shoot Cicada, but not before he threw his dagger full of energy towards them leaving them out of battle, and just as he was prepared to stab Barry with his dagger, Killer Frost emerged and fired an ice beam at him, sending him flying into a nearby van. He quickly stood and escaped the scene. The team later realized that Frost is immune to Cicada's dagger and could be useful in defeating him.
Killer Frost and Elongated Man were sent to Ivo Laboratories to help deal with A.M.A.Z.O., who had been accidentally activated by an inexperienced Oliver Queen using Barry's speedster abilities. The two and Officer Jones were unfortunately not strong enough and as they were floored by the android, it absorbed the two meta-humans' abilities, using Frost's abilities to fly through the roof and escape.
After traveling to Gotham City, Kara Danvers used Caitlin to gain access to Arkham Asylum, convincing the nurse that she was a mentally ill meta-human, even quickly flashing Frost's eyes. After they got inside, a riot began and the two split up. Eventually, Caitlin came across a frantic Nora Fries who was searching for something amongst the shelves. When Caitlin attempted to help her, Nora blasted a beam of cryogenic smoke at her, causing Killer Frost to emerge and engage in a fight. When Nora grabbed her husband's cryo-weapon, Frost asked for some assistance over her comms but before Barry or Oliver could arrive, Nora blasted her back through a table, knocking her unconscious. Upon waking, Caitlin noticed that Oliver and Barry were fighting each other, for what she called help, when Batwoman neutralized them and made them realize that they were exposed to a hallucinogenic gas.
After finding the Book of Destiny, Caitlin, Felicity, and Curtis began to examine it to find a way to open it, but suddenly the Book disappeared in a blue smoke, leaving Caitlin and the others confused.
After John Deegan used the Book of Destiny to rewrite reality and made himself "Superman", Caitlin and Killer Frost's lives were rewritten. It appeared that Frost had fully taken over and worked under Deegan as one of his prime soldiers. After he returned to his base, Frost and John Diggle applauded his actions but he quickly made them stay quiet and exclaimed that the Trigger Twins had escaped him. Diggle and Frost quickly assured him that they would be captured just as a warning from the pipeline alerted the room. Frost explained that it must have been "Subject 1" but "Superman" quickly explained that he would take care of her himself.
Later, Frost traveled down to the pipeline to speak with Agent Danvers and asked her to go home but became skeptical when she refused. She asked if she had boyfriend trouble but Alex just explained that she thought the work they do is important and she wouldn't change. Frost simply shrugged and left the pipeline. After Kara had managed to get through to Alex, the two attempted to escape Deegan's base but were confront by him, Frost and Diggle. However, a breach opened and Barry, Oliver and the real Superman came through and the two supermen broke through the ceiling and began their fight while Diggle and Frost fought Oliver in the elevator. The two were ultimately beaten by him and thrown in the pipeline. This reality was later returned to normal after Superman used the Book of Destiny to repair it.
Caitlin assists in the fight against the different Cicadas with the second one killing her father. Later, Caitlin and Cisco managed to create a meta-human cure to prevent meta-humans from being hunted and killed by the new Cicada.
Meeting an old colleague
Caitlin is troubled by her colleague, Ramsey Rosso, whose attempts to cure himself of a rare disease causes him to mutate into a dark matter-empowered monster who nearly takes control of Central City.
During the Anti-Monitor Crisis, Caitlin as well as everyone in the multiverse except for the seven Paragons, was killed in an antimatter wave by the Anti-Monitor on December 10, 2019, only to be restored a month later, after the Paragons and the Spectre created a new universe.
According to Craig, a member of Savitar's cult, Caitlin would have been described as being "glorious and powerful", and Savitar had "special plans" for her, which did come true as she helped him and he needed her to kill Black Flash.
When Barry visited a possible future, in the year 2024, it is revealed that Caitlin allied herself with Savitar. Moreover, during a climactic battle, Vibe's arms were frozen and shattered by Caitlin, forcing him to replace them with bionic arms and subsequently making him unable to use his powers. Caitlin, still as Killer Frost, has been locked up in Iron Heights, and still refuses to divulge the identity of Savitar, with Julian as her caretaker.
Defeating the Anti-Monitor
- "Do you know why he's like this?"
- "And now, so do you."
- —Caitlin Snow and J'onn J'onzz, as the latter restores her memories[src]
In January 2020, Caitlin helped nurse Harrison Nash Wells back to health just as J'onn J'onzz entered S.T.A.R. Labs and restored her memories of the Crisis. She then turned on Nash, exclaiming that it was his fault the crisis occurred and once J'onn also restored his memories, Nash agreed.
Later, when Mobius returned to continue his fight, Frost, Heat Wave and Black Lightning defended S.T.A.R. Labs from Shadow demons. After the Anti-Monitor had been defeated by the Crisis team and the shadow demons disappeared, President Shaw thanked the heroes on live television as Caitlin and Barry watched from S.T.A.R. Labs. The entire United States then had a moment of silence to honor Oliver Queen's sacrifice.
War against Black Hole and Mirror Monarch
After the demise of the Speed Force, Caitlin and Cisco created the Speed gauge and explained to Barry how it records his usage of his remaining speed force, recommending to him to use what remained wisely.
Soon, Nash Wells started yelling to be free of the pipeline; Frost used a scanner in its 3D mode to learn the secret of Harrison Nash Wells' mind. Eobard Thawne then tricked the three, knocking them unconscious, to escape momentarily but he was quickly caught by Barry. Caitlin chastised Barry not only for using his speed, but for contemplating and almost killing Nash's body to get to Thawne. Caitlin's constant arguing insulted Barry enough to finally leave the area. As Cecile arrived to help exorcise Thawne, Caitlin turned to Frost to deal with a call from Mercury Labs.
Caitlin was able to take control from Frost after the latter worked with their mother in temporarily stabilizing the wound and finding their baseline. Caitlin talked with Barry about the death of Joseph Carver and how much he missed his wife, to which Caitlin reminded him that he was the paragon of love and that would provide the answers he seeks. They hugged farewell as she prepared to go north to heal.
A few days later, Barry called Carla so she could give Caitlin and Frost an update on recent events.
Frost moves in
Team Flash volunteer at a construction site after the destruction caused by Eva McCulloch. Caitlin tells them about her recurring headaches. Somehow, Caitlin and Frost separated by then unknown means and they went to show Cisco in the S.T.A.R. Labs.
They asked Cisco what had happened but he was shocked, as were the other members of Team Flash. Caitlin eventually discovered that exposure to the Mirror Monarch's rays caused Frost's cells to replicate enough to create a new body, separating their telepathic connection so that they could no longer hear each other's thoughts. Cisco would use the Firestorm Matrix to put them back together, but Frost sabotaged the object, making Caitlin angry. Frost later revealed that she wanted to live her own life.
Caitlin with a painting in her hand enters her apartment to find Frost there, making a painting; Frost says that she had Matthew Norvock bring her things from storage. Frost is making the painting because there is an empty wall where she wants to place it; Caitlin retorts that great minds think alike and place the painting she brought on the wall. Frost inspects it and finds it lacking until she puts her own flare on it. Caitlin sighs.
When a wave of green energy hit Central City, Caitlin and Frost leave the apartment and go to S.T.A.R. Labs; the energy has changed Caitlin's outfit. Caitlin researches the energy and explains to Joe West when he arrives that the energy is from a Force of Nature and is spreading.
Protecting her twin
Caitlin has been upset for days as she feels that she is powerless to help her "twin"; Frost has plead guilty and gone straight to sentencing with Kristen Kramer talking the District attorney into wanting to give Frost the meta-human cure for her crimes, which might kill Frost.
Caitlin, Cisco,and Allegra Garcia devise a plot to destroy the samples that the CCPD has to make them ineffective. Caitlin tells Officer Daisy Korber that Caitlin is missing property from when she was arrested; while Daisy gets the proper forms, Allegra creeps into the inner chambers as Cisco puts the camera in a video loop. Allegra gets stopped by Kristen unexpectedly, so Caitlin distracts Daisy again and goes into the inner chambers. Before the loop expires, Caitlin succeeds in contaminating the cure.
When everyone goes to court though, Kristen had other samples of the cure developed by A.R.G.U.S. and tells the judge that Frost must have destroyed the previous ones; Caitlin admits before the court that she was the saboteur. Carla Tannhauser is called and verifies that the cure would not kill Frost.
Frost and Caitlin talk. Frost has decided on jail time, but Caitlin wants her to take the cure and keep her freedom. Caitlin says that all of her life she has been with Frost; she does not want to be without her sister. Frost, though touched, explains that, as an individual, she must be allowed her own fate.
Analyzing the Forces
The next day, Caitlin still hurts from losing Frost, but she uses work to distract her by analyzing the body of Alexa Rivera. While attending Alexa, Caitlin sees Alexa's body suddenly move as a tremor occurs; Iris and Barry run into the med bay and ask questions. Caitlin witnesses as the married couple touches Alexa and resurrects her. Caitlin immediately begins reading vital signs. Caitlin helps to explain to Alexa that she was resurrected because she shared the "cosmic DNA" that Iris and Barry carry, making them her "parents" in a meta-human, cosmic power sense.
Barry proposes to have Alexa train in the use of her powers, so Caitlin and Cisco prepare the test area for Alexa's transformation with Caitlin watching vital signs. Alexa does not have control over being Fuerza; Caitlin is forced to explain this to Barry that he is pushing Alexa too hard, too fast, citing Eobard Thawne as an example of a slow-training mentor. Caitlin gives Alexa a cerebral inhibitor and explains to her about Caitlin's past relationship with Frost and how she grew to accept her split personality. Overhearing the conversation causes Barry to apologize to the women.
Fightning the Godspeed clones
Caitlin is very intelligent and passionate about her work as a bio-engineer and scientist, occasionally becoming excited at the possibility of observing supernatural biology in meta-humans. She is generally a very compassionate and caring woman and is determined to help others through her work. Caitlin loved her fiancé Ronnie Raymond very much, stating that he knew how to make her laugh. She and was devastated by his apparent death, which sent her into a state of depression for almost a year. As a result of this she, didn't smile much. However, since being brought onto the team, working with Barry Allen, helping people and saving lives, she has started to liven back up. She has shown great concern for Barry as she often advises against engaging meta-humans they know little about and was initially against Barry using his powers as a guardian angel for Central City, though she eventually grew to accept and even participate in it.
Caitlin is also seen to be somewhat "guarded", in her own words, and timid as seen when she was terrified of going into the S.T.A.R. Labs particle accelerator it being the location of Ronnie's supposed death, though she later overcame this obstacle with Barry's support, becoming more assertive, brave and confident. Despite them being quite different in personality, she is also close friends with Cisco Ramon but finds his need to nickname every meta-human they face annoying, although she has occasionally nicknamed a meta-human now and then herself. Leonard Snart considers Caitlin to be "uptight", which his sister agrees with. When Caitlin was reunited with Ronnie, alive and well after he was separated from Martin Stein, she was overjoyed, no traits of her initial depressive, forlorn personality remaining. When she finally marries Ronnie, she is perfectly content accepting that everything she's experienced over the past year, leading up to wedding the man she loves has been worth it. When Caitlin loses Ronnie again, this time for real, Caitlin is devastated, so much she is unable to stay in S.T.A.R. Labs as she blames herself for his death. However she has slowly managed to recover and regained her desire to help Team Flash.
Though not as prominent as her other traits, Caitlin has a somewhat flirtatious side to her personality. Often when flustered or uninhibited by the effects of alcohol she can become silly, frazzled, and hinted a few times during her night out at the dive bar with Barry that she dropped many hints that she was interested in Barry. After meeting Hunter Zolomon, masquerading under the name "Jay Garrick", he and Caitlin have quickly become infatuated with each other, their infatuation developing into a relationship. Caitlin's love for Hunter was the driving force for her to find a cure for his condition. However, after the revelation of "Jay Garrick" as the man behind the mask of Zoom, Caitlin did not allow her feelings to cloud her judgment on Zoom's misdeeds, rightfully recognizing him as "nothing but a monster" and refusing to accept Hunter's lingering affection for her. Nevertheless, Caitlin called upon those feelings, her face in tears, when she tried to influence Hunter to show his merciful side, sparing Barry Allen from certain death.
Caitlin is shown to be extremely Naive when it comes to men (with a pretty face, huge muscles and shining teeth) and trust. Like when Barry refused to trust Jay Garrick (a stranger from another Earth that they know very little of), Team Flash (especially Caitlin) quickly did. And that resulted not only Team Flash being betrayed again, but also resulted Barry's father getting murdered in the same place, in the same way. Then when Ralph Dibny's name popped up as one of the metas on the bus, she was showing sympathy toward him despite the fact that even though he didn't deserve it, Caitlin doesn't know Ralph like Barry does and she hasn't even meet him.
After her imprisonment with Hunter, it seems that Caitlin began suffering from post traumatic stress disorder (PTSD), due to her former lover and his frightening behavior and repeated displays of violence in front of her, seeing visions of Zoom when he's not there, and questioning if she still has her sanity.Since Caitlin has been developing cryokinetic abilities like her Earth-2 counterpart she has been terrified of becoming just like her. While reluctant to tell her friends she has used these powers to aid them occasionally without them knowing, but has gradually realized her inability to control them. This has made Caitlin very terrified but as a result of her changing biology she has become increasingly temperamental, which causes her appearance to become more like her Earth-2 counterpart. However, Caitlin is still sane enough to realize this but is only more horrified at her increasingly inability to manage her emotions. However, her desire to retain her humanity and her biology changing to make her more "cold", seems to be causing Caitlin to develop dissociative identity disorder.
- "Right. I'm the queen of letting these people down. But you know what? They're still here. No matter how much I disappoint them, they still show up for me. I don't really understand it, but I think that's part of this whole friends thing. So, unless you do something worse than kidnap and stab them, I think you're gonna be just fine."
- —Killer Frost to Ralph Dibny[src]
Worrying about her new-found, uncontrolled powers, Caitlin's emotions become heightened enough that she became a vindictive, angry and cruel individual, similar, but not identical to Frankie Kane's split personality disorder. Also like Frankie, when affected by her powers, her eyes glow pale blue (while Frankie's glow pink). However, while Magenta tried to get rid of the Frankie persona altogether, Killer Frost state amplifies Caitlin's own fears, insecurities and bitterness. As Killer Frost, she mocked Barry by mentioning his most horrible failures including the deaths of his mother, father, Eddie and Ronnie, as well as revealing to Cisco that his brother, Dante was alive in the pre-Flashpoint timeline, before Barry changed it. She expressed bitterness over Barry only caring about himself and his own happy ending, while she was left broken.
Caitlin also mocked Cisco by calling him pathetic for feeling sorry that he had to hurt her to save Barry. She openly blamed Barry for what's happened to her, yet admitted that she feels broken. She nearly killed Julian and one of Alchemy's Acolytes, however she was still unable to kill Barry, making her snap out of her anger, as she became horrified at what she almost did.
Once Killer Frost was fully awakened due to Caitlin's temporary death and revival, she states that she doesn't want to be cured and wants Caitlin never to come back. She allies herself with Savitar after he reveals himself to her.
Killer Frost went after Tracy Brand after Savitar promised that if she lives up to her name and murders Tracy, she could be a god. She arrived at CCU in her new outfit and attacked Barry and Cisco, but when Barry fought back with fire, she ran away. She then attacked Tracy for the second time outside Jitters and continuously formed an ice slide that she slid on for a while without any difficulty. She took advantage of the fact that Cisco would not hurt her and almost hit him with a blast that Barry took. She stabbed Barry in the leg so that he couldn't follow her and she left, claiming that this is her now.
Later, Killer Frost kidnapped Joe's girlfriend Cecile outside of Joe's home and threatened to kill her if Joe and the team did not hand over Tracy to her and Savitar. Later at the supposed exchange site, she claimed that killing Cecile would bring her no joy but Tracy's death at her hands would. When Barry tried to talk her out of it, she knew exactly what Barry was going to say. She and Cisco later faced off, and while she seemed calm at first, she later fought back as hard as she can and lost to him. Cisco managed to get a sample of her blood, which could be the key to making a cure for her. Before Cisco can take her, Savitar arrived and took her away.
Despite all this, while reluctantly working alongside her former allies, it was shown she still has a strong attachment to her memories of working at S.T.A.R. Labs when she and Cisco reminisced about Ronnie losing his temper back when they were trying to build the particle accelerator. However. Killer Frost also showed in this moment that thinking about who she used to be made her uncomfortable as she quickly, sullenly, stated that she didn't want to stay any longer than she had to. Her conflicted feelings about herself and her old allies was again emphasized when she told Team Flash she never loved them and left, only for the assertion to hurt her heart enough to cause the real Caitlin to emerge for a few seconds once she was out of the team's sight.
Despite her continued allegiance to Savitar, Caitlin began showing signs of regret and doubt in her betrayal. During the final confrontation of Team Flash and Savitar, Cisco's unceasing loyalty for Caitlin finally enabled Caitlin's true-self to become permanently restored and reconciled with her friends. At the same time, she felt lost, unsure of who she is now.After her experiences with Amunet Black, Caitlin began to realize that she could co-exist with Killer Frost and started treating her alter-ego as a friend and teammate rather than an adversary. Though their relationship was slightly tenuous at first, Caitlin began to develop better control over her powers and accept her alter-ego as a part of her. To which, Caitlin was devastated when her powers were apparently taken away by Clifford DeVoe and determined to find a way to restore Killer Frost.
In the future in which Iris dies, by the time of the year 2024, Caitlin has become too far gone to the point where she refuses to be called real name, as she prefers being called by her alias "Killer Frost", she becomes angry when people call her by her real name, despite her insanity and cold nature, Caitlin is very observant, she was able to realize that the Barry Allen she was speaking to was the younger-self of her Barry; due to the look on his face, as the latter had not yet become emotionally broken, as his Iris was not dead yet. This future was later erased when Savitar killed H.R. instead of Iris.
Powers and abilities
- "Persistent sub-thermal homeostasis with, uh, involuntary gelid substantiation. She gets cold and freezes stuff."
- —Kara Danvers on Caitlin Snow's meta-human powers[src]
- Meta-human/Cryogenic physiology: After Caitlin's father, Thomas Snow, discovered that she had the genetic marker for ALS, he used experimental cryogenic gene therapy on her to prevent the ALS from manifesting in her. The alterations Thomas had made to the treatment resulted in Caitlin developing a dual-personality (i.e. Frost) and meta-human abilities soon after he treated her. Caitlin's Frost persona, and the abilities associated with her, remained dormant for 17 years (apart from a few brief episodes during her childhood), as several tests never showed signs of a meta-human gene. Three years after the S.T.A.R. Labs particle accelerator explosion, Caitlin's powers finally emerged fully. After defeating Mirror Monarch, both Frost and Caitlin suffered from immense recurring headaches, which seemingly led to them becoming separated from one another and Frost inhabiting a body of her own. It was later revealed that Eva's mirror gauntlet contained a reflective mirror chip that forced Frost cryogenes to rapidly replicate and create a whole new form so she could survive. This made Caitlin still have her medical knowledge and Frost have her ice powers
- Transformation: After Caitlin and Killer Frost decided to be just one, Caitlin became able to transform into Killer Frost and vice-versa; for example, she remembered her anger against her childhood bully and cut her hand with a broken bottle (which healed immediately) to trigger her alternate personality. Caitlin's transformation affected her physical appearance, as it turned her hair white/grey and changed her eye color to an icy blue.
- Thermokinetic cryokinesis: By absorbing thermal energy from molecules to create gelid surroundings, Caitlin could generate dangerously low temperatures from her body, letting her freeze virtually anything. She could thus create sheets of ice, or shoot spear-like icicles at opponents. Caitlin could also create an ice slide and use her cryogenic powers to rapidly propel herself forward on the slide. Furthermore, her powers could reach such low levels that they could completely negate a speedster's healing powers and alternatively neutralize accelerated decomposing; by generating temperatures as low as -360 degrees, she proved able to shatter beings as powerful as the Black Flash. During the tests run by her mother, Caitlin was able to rapidly freeze a solid shaft of tungsten heated to over 2,000 degrees centigrade. She often gestured when using her powers, but she could freeze things by touching them (e.g. Caitlin could freeze people through a kiss) or by being in the same general vicinity. She was also able to freeze the light-based bullet from photon rifle in order to remove it from her body.
- Energy absorption: Caitlin was able to absorb the thermal energy from molecules to generate low temperatures from her body, basically making things freeze, this was mentioned when Carla notice that not only was she freezing the weapon, she was also absorbing it's energy as her own.
- Cryokinetic breath: Caitlin was able to exhale cold mists with enough momentum to knock several people backwards and off their feet. She could also use this as a means to produce a thick and obscuring fog.
- Cryokinetic constructs: Using her thermokinetic cryokinesis, Caitlin could create constructs made of ice and icicles as shown in multiple occasions. During the Earth-X invasion, Catlin was able to create ice swords to fight the Nazis and we also see Frost uses ice daggers as her main weapon to might opponents such as her fight with Cicada and her fight with Grace Gibbons, Caitlin was wielding two daggers and was able to go toe to toe with Grace but was overpowered.
- Cryokinetic healing: Caitlin was able to heal injuries by filling the wounds with ice. As the wound heals, the ice will thaw until its fully healed, the ice will be melted by the time its healed. For example, when she used this ability to help with Cisco's hand after Cicada's dagger cutted him, closed up Cicada's chest wound after removing the dark matter shard, and when Joe was injured by Ramsey's zombies.
- Limited atmokinesis: Caitlin's powers could also affect the weather around her, dropping the climate of the area and causing it to snow.
- Flight: By generating cryogenic thrust, Caitlin was able to propel herself to the wall and then, to the ground to avoid herself from falling. Another instance is when we seen Caitlin propel herself into the air to fight her father's alter-ego, Icicle, by creating ice slides and she used this ability before when she took on The Flash while trying to kill Tracy Brand.
- Cold immunity: An added benefit to her powers, Caitlin's cells could withstand subzero temperatures, as seen when she was unaffected by a snowstorm she created after escaping S.T.A.R. Labs and later when Icicle decreased the temperature in a lab to absolute zero.
- Accelerated healing factor: While Caitlin was accessing her powers, her metabolic rate was augmented to offset cold tissue destruction, allowing her to regenerate from damage sustained on her body at a rate much faster than even a speedster; however, foreign matter had to be taken out in order to not impede the healing. After clinically dying from a combination of a seizure and her reopened impalement wound, she was immediately resuscitated into a stable and cognitive state while her wound seamlessly healed completely in seconds. However, her healing powers only worked when her Frost side took over, as wounds inflicted by Amunet Black left Caitlin bruised and requiring stitches. Her healing was strong enough to even able to withstand a photon blaster that was able to disintegrate a person in seconds.
- Superhuman durability: Caitlin had remarkable durability, seeing as she tolerated substantial amounts of physical distress; for example, she survived being hurled into a car and electrical box by Vibe's concussive blasts without sustaining any serious injury.
- Mental communication: Caitlin and Frost were able to talk to each other whenever one of them was in control.
- Transformation: After Caitlin and Killer Frost decided to be just one, Caitlin became able to transform into Killer Frost and vice-versa; for example, she remembered her anger against her childhood bully and cut her hand with a broken bottle (which healed immediately) to trigger her alternate personality. Caitlin's transformation affected her physical appearance, as it turned her hair white/grey and changed her eye color to an icy blue.
- Velocity X enhancement: After injecting herself with Velocity X, Caitlin gained the powers of a speedster.
- Electrokinesis: Like all speedsters, Caitlin could generate electricity from her body, which was blue in color. Due to having mastered her ice powers, (and possibly also from experiencing Flashtime before), she adapted to her newfound speed immediately. She was able to generate her remaining Velocity lightning on command, and unleashed a powerful lightning-enhanced cryo blast.
- Superhuman speed: While her speed was not measured, she was able to keep up with and even outpace the Flash, who is able to run well over Mach 13, and was freshly recharged from the artificial Speed Force. Though she outpaced Flash due to having a similar familiarity with Central City and using her ice powers to slow him down, Flash was presumably running at his top speeds against her, noticeably exerting a lot of effort to phase and dodge her ice blasts.
- Superhuman agility: Caitlin was incredibly agile, able to change direction immediately. She was able to make sharp turns on city streets while moving at super speed without sliding or losing her balance, and simultaneously use her ice powers, even on vertical surfaces, to create ice walls and ice blasts without slowing down.
- Enhanced durability: Caitlin was able to get up with little to no injuries after being sent flying through the air and crashing into a car from an extremely high height. This was due to her already superhuman durability and her body adapting to the Velocity speed boost.
- Superhuman reflexes: Caitlin's increased speed also augmented her reaction time, allowing her to react to danger and events far faster than a normal human.
- Superhuman stamina: Caitlin's body could handle the stresses of superhuman racing without noticeable distress, and her body's enhanced stamina allowed her to function much longer than a normal human without becoming tired or weak.
- Genius-level intellect/Master scientist/Physicist: Caitlin is extraordinarily intelligent, gaining a PhD and two doctorates by the time she was 28 and being a promising bio-engineer at S.T.A.R. Labs. Her talents have been a crucial aid in creating the particle accelerator and helping Team Flash. Working together, Caitlin and Cisco Ramon were able to use a sample of the Mirakuru to create a cure for it. Caitlin was also able to create new Velocity serums for "Jay Garrick" that temporarily healed him. She also somewhat understands the features of the Speed Force. Using samples of Cicada's dagger, Caitlin and Cisco successfully synthesized a meta-human cure.
- Computer specialist: As a member of S.T.A.R. Labs, Caitlin has some technological skills of note, albeit not her main area of expertise. This is evident in her ability to reprogram the S.T.A.R. Labs satellite to track meteorological abnormalities over Central City in order to locate Clyde Mardon. Caitlin was able to determine that Ramsey Deacon's powers produced an organic virus and helped Cisco create a compound to invert it.
- Medical knowledge: Caitlin is accomplished in multiple fields of medicine and acts Team Flash's medical support, such as monitoring Barry Allen's condition while he was comatose. Caitlin was also able to cure Barry when he was poisoned by Kyle Nimbus and treat his grievous injuries from Tony Woodward, including setting Barry's shoulder back into place. She also patched up Eobard Thawne after he was brutally beaten up by his Reverse-Flash speed mirage. Caitlin once mentioned that she knows how to perform a lobotomy, a procedure that requires both training and skill in the field of neurosurgery. Apropos, she had the ability to potentially surgically extract a thermite bomb from Lisa Snart's head. Caitlin also trained in obstetrics, as shown when she monitored Cecile Horton's pregnancy after the latter gained meta-human powers. Caitlin was even able to successfully deliver Jenna West at S.T.A.R. Labs.
- Skilled hand-to-hand combatant: During the six months in which she worked as an enforcer for Amunet Black, Caitlin as Frost developed a measure of sheer hand-to-hand combat skills to a yet-to-be elaborated degree. She once reversed an arm bar Norvock exerted upon her, slamming and pinning him painfully against a pinball machine. Caitlin also managed to hold her own against and even briefly injure Orlin Dwyer. She fought on par against an older Grace Gibbons for a while, but was eventually overpowered. She was able to fight zombified patient at a hospital with ice brass knuckles and later fight a group of zombies with Joe.
- Skilled swordswoman: During the Earth-X invasion, Frost was able to create ice swords and take down multiple Nazis with ease.
- Expert markswoman: Caitlin has incredible proficiency with guns, able to accurately subdue Geomancer by firing the B.O.O.T. at him. Caitlin also displayed excellent accuracy when armed with a Cold gun, able to incapacitate a riled-up Barry running wildly around S.T.A.R. Labs after he gained enhanced super-speed, something even Cisco was unable to accomplish with his vibrational blasts. After Clifford DeVoe seemingly took away her powers, Caitlin began occasionally using the Cold Gun as her primary weapon of choice when operating in the field.
- Expert knife wielder: During a fight with Cicada, Frost used a dagger as a weapon, managing to injure him.
- Indomitable will/High tolerance for pain: Caitlin has a remarkable level of endurance; despite sustaining grievous injuries from an attack by Abra Kadabra, she was able to maintain consciousness throughout her surgery while instructing Julian Albert in removing the shrapnel from her body. Also, after being brutally pummeled into unconsciousness by Amunet, Caitlin was able to recover enough to flee when Amunet was distracted and stitch up her own injuries. During a battle with an older Grace, Caitlin managed to keep fighting despite the former inflicting multiple injuries on her arms until being overpowered. She even eventually overpowered Frost's violent impulses and used her compassionate nature to begin coexisting with her alter-ego.
Alternate reality abilities
- Peak of human physical condition: As a henchwoman of Superman, Frost was in top physical condition.
- Expert hand-to-hand combatant/Martial artist: Frost was a highly skilled hand-to-hand combatant and martial artist; she was able to overpower Oliver Queen with help from John Diggle when Oliver had lost his abilities.
- Carbine: Caitlin has implied that, similar to her Earth-2 counterpart, her powers have no effect on carbine.
- Power-dampening tech: Like most meta-humans, if Caitlin is wearing power-dampening cuffs, she can't use her powers. She can also be contained in a power-dampening cell.
- Doctor Light's photon rifle: When she was shot with Doctor Light's photon rifle, which was lethal to everything it touched, it created a wound that troubled Catilin's accelerated healing, and after battling Sunshine the wound opened back up and worsened its effects.
- Abnormally high temperatures: Intense heat can apparently negate Frost's powers. However, the super speed she gained from Velocity X didn't negate her powers, since her thermogenic cryokinesis negated the heat that she generated.
- Flashtime: Frost can't use her powers while moving at high speeds since this causes friction between her atoms, which generates extreme heat under these circumstances. Put simply, she is not able to access her powers because Flashtime is an external source of speed, rather than an internal one that can be counterbalanced.
- Nucleokinesis: It is likely that similar to her Earth-2 counterpart, Caitlin or Frost can be severely injured, even killed, by nuclear energy.
- Borderline split personality disorder: Caitlin's changing biology also caused physiological effects. The more she would use her powers, the crueler and more sadistic she would become, showing no emotional attachment or regard for human life. While struggling to contain her powers, Caitlin developed a form of dissociative identity disorder which is triggered when angered, making it difficult to calm her down and restore her rationality. The change can be seen as the case of Caitlin's super-powered alter-ego weakening in her psychic apparatus, allowing for her hidden fears, grudges, and insecurities to come to the surface, rather than a true split personality. Over time, her friends continued trust and love for her finally allowed Caitlin to overcome her mental struggles, regaining her sanity while having full control over her powers. However about six months later, having taken Julian Albert's serum to cure her, it proved only temporary and had an additional side-effect of developing a complete separate personality. In addition to the changes happening more suddenly and erratically both ways, it also caused both the Caitlin and Killer Frost side to no longer have any recollection of the other's actions. After some words of inspiring encouragement from Iris West, Caitlin and Killer Frost decided to just be the same person and Caitlin no longer had a problem with her alternate self. Killer Frost eventually started to care about Caitlin and was even concerned for her when faced with the threat of a nuclear explosion.
- Emotional state: Caitlin's transformation into Frost is only triggered whenever she is angry or scared, as her split personality requires the surge of heightened adrenaline in her system. However, after Caitlin reunited with Frost following the battle with Icicle bonded with her, she has overcome this weakness and is able to call on her alternate persona whenever needed.
- Julian Albert's serum: Julian worked with Caitlin's mother, Carla Tannhauser to create a serum capable of removing Caitlin's powers. According to Caitlin, while the serum initially seemed to work, Killer Frost re-emerged sometime afterwards, stronger than before, and was no longer affected by the serum.
- Limited/Unstable control of powers: According to her mother, the continuous use of Caitlin's powers would end up making her unable to "turn them off", leading to Caitlin accidentally freezing her laptop. Caitlin seemingly began to use her powers (in small doses) with little to no adverse effect, as shown at Christmas 2016 when she made it snow. A tell-tale sign of her powers overwhelming her are the physical changes she gradually gains from them, such as her hair turning white and lips turning blue. The most noticeable sign of her losing control is her eyes glowing a pale whitish-blue and her distorted voice. The physical changes become more prominent as she makes use of her abilities, though they will recede if she goes long enough without using them, such as her hair going from white back to its original chestnut brown. However, as Frost she is in full control of her powers, to the point where she was able to create a slide of ice to ride across the city. Caitlin is now able to control them through her Frost side, who has become her ally.
- Mental blockage: While battling Clifford DeVoe/The Thinker after he took over Ralph Dibny's body, DeVoe seemingly used Matthew Kim/Melting Point's powers to take away Caitlin's Killer Frost powers. However, Caitlin later found out that Killer Frost was still inside her without the presence of dark matter in her system; she just needed to find a way to make Killer Frost re-appear. Killer Frost later resurfaced during a battle against her father, Thomas Snow's evil second personality, Icicle, to save her friends. Shortly thereafter, Team Flash realized that DeVoe hadn't used Melting Point's powers against her at all, but instead Dominic Lanse/Brainstorm's powers to place a mental blockage in her mind to keep her from accessing her Killer Frost personality. After discovering this, Caitlin began using the cerebral inhibitor to help herself get back in touch with Killer Frost, although Team Flash suspects that, with time, she should be able to reach Killer Frost again without use of the cerebral inhibitor. After a week Caitlin and Killer Frost is able to talk and switch body's again without the use of the instrument or presence of stress.
- Frost suits: Caitlin wears a protective suit as her alter-ego, Killer Frost. Upon gaining full control over her powers and aiding her friends in the final battle against Savitar, she stopped wearing it. However, after her Killer Frost side returned, Caitlin started wearing a baby blue jacket with leather bottoms. After Frost returned from her disappearance, she never gained an official suit at first, mainly just wearing black, until Cisco created a new, dark blue suit, similar to her first suit.
- Power-dampening cuffs: After her powers began manifesting, Caitlin initially wore a pair of Cisco Ramon's power-dampening cuffs on her wrists as a means to help keep her powers in check due to her unstable control over them. However, she abandoned the use of these when she couldn't keep them charged for long periods of time and would have to sit with them plugged in, which she claimed made her "feel like a human tablet".
- Solar power collection pendant: Julian Albert created a snowflake-shaped pendant designed to dampen Caitlin's powers, as well as collect solar energy in order to charge it whenever she went outside so that it continues to work without constant recharging. After Julian removed it to allow Caitlin's meta-human powers to heal her injuries, Killer Frost destroyed it.
- Cold gun: After Caitlin lost her powers, she started using a version of the Cold Gun when in the field, though stopped once regaining Killer Frost.
- Ice throwers: Alternatively called "Frost Bites" by Barry Allen (although Cisco preferred the term "ice shooters"), Caitlin used these wrist-mounted cryogenic blasters to rescue Clifford DeVoe's hostages. Since she has regained Frost, Caitlin doesn't need to use her ice throwers.
- Cerebral inhibitor: Caitlin used the cerebral inhibitor to bypass the mental blockage placed in her mind by DeVoe to talk to Frost. After a week of using the inhibitor, Caitlin and Frost were able to talk and switch between active personas without the use of the device. When Nora West-Allen was stuck in Grace Gibbons' mind, and Barry Allen and Iris West were stuck in Nora's, Caitlin used the inhibitor to communicate with them until the device began overheating, forcing her to stop.
- Frost suit: Caitlin wears a protective suit as her alter-ego, Killer Frost. After Frost returned from her disappearance, she never gained an official suit at first, mainly just wearing black, until Cisco created a new, dark blue suit, similar to her first suit.
DC's Legends of Tomorrow
Freedom Fighters: The Ray
The Flash: Season Zero
The Chronicles of Cisco
Crisis on Infinite Earths
- Interestingly, many villains in the series have expressed a degree of fondness towards Caitlin;
- Eobard Thawne often expressed his admiration for her abilities.
- Hannibal Bates displayed an attraction to Caitlin, notably when he was staring at her curvature and then kissed her while disguised as Barry Allen.
- Hunter Zolomon was in love with her, which was mutual until Caitlin learned of his true nature.
- Grodd has expressed genuine gratitude towards Caitlin and she is one of the few humans, including Eobard, whom he hasn't tried to harm.
- Savitar has considered Caitlin like a child of his.
- Amunet Black has shown admiration for Caitlin and her skills as a doctor.
- Mick Rory developed a crush on her after seeing her as Killer Frost.
- Icicle wanted Caitlin's alter-ego, Killer Frost, to be like him.
- Caitlin has been kidnapped in every season of except season 3, more times than any other character.
- In Season 1, she was kidnapped by Captain Cold and Heat Wave so that they could get to The Flash in "".
- In Season 2, she was kidnapped in "" and "" by Grodd and Hunter Zolomon, respectively.
- In Season 4, Caitlin was kidnapped by Amunet Black, The Trickster, and Siren-X in "", "", and "", respectively.
- In Season 5, she was kidnapped by Icicle in "".
- Caitlin likes the show Orange Is the New Black.
- She enjoys Mai Tais.
- Ironically, Caitlin is bad at Operation, since it's “not even remotely anatomically correct.”
- Caitlin carries a blood collection kit in her purse wherever she goes.
- According to Caitlin herself, she practiced the Hippocratic Oath repeatedly as a child.
- She likes funnel cake.
- Caitlin has two doctorates and a PhD.
- She is good at laser tag.
- She likes the color pink.
- Caitlin's measurements are 34-25-34, according to Ralph Dibny.
- Like her father, Thomas, Caitlin loves peanut butter and jelly waffles for breakfast.
- In an erased timeline, Caitlin is the first person to discover that Dr. "Harrison Wells" isn't paralyzed after she discovers his wheelchair vacant while they are at CC Jitters. However, due to Barry changing the timeline, Caitlin learned the truth eventually along with everyone else.
- In a second erased timeline, Caitlin, along with everyone in Central City, was killed by Vandal Savage using the Staff of Horus in his efforts to kill Carter Hall and Kendra Saunders. However, Barry changed the timeline so this disaster never occurred.
- Apparently, Caitlin Snow doesn't exist on Supergirl's Earth. However, as shown by Jay Garrick being Henry Allen from Earth-3, doppelgängers do not necessarily always have the same name.
- Caitlin has had three love interests as listed in order: Ronnie Raymond, "Jay Garrick", and Julian Albert. She has also shown an attraction towards Eddie Thawne and Oliver Queen and is hinted to have feelings for Barry.
- After Ronnie's death, Caitlin was in two relationships, first with Hunter Zolomon and then with Julian Albert. Caitlin initially believed that Hunter was a hero on Earth-2 while Julian was a crime scene investigator for the Central City Police Department. Barry, Hunter, and Julian all balance between two types of people: a civilian and a hero.
- Additionally, Hannibal Bates and Mick Rory have expressed an interest in Caitlin.
- While Caitlin was revealed to have powers, some of the struggles she went through are similar to Siobhan Smythe/Silver Banshee. Both were scared about having powers, went through great stress before and after they manifested, and had trauma brought upon them due to Cisco and Winn Schott, respectively, not being trusted in keeping these secrets from others over what they know is right and wrong.
- The only difference between the two turning to the dark side is that Siobhan was able to maintain her mental stability by quickly embracing her powers, furthering her sense of optimism while Caitlin initially could not because she feared becoming her doppelgänger and hurting her friends.
- Caitlin shares several similarities with Earth-2 Laurel Lance; the loss of the men they loved and the manifestation of their powers each played an important role in the two women's descent to darkness. They both used memories of their known civilian personas to torment Team Flash and Team Arrow. However, the women's regard for the heroes managed to redeem them; Caitlin's love for her friends enabled her to overpower and eventually come to terms with Killer Frost, staying away from the darkness. Laurel gradually began to genuinely care for Team Arrow after their numerous attempts to protect her, ultimately leading her to turn on Ricardo Diaz.
- Caitlin has a drink named after her alter-ego at CC Jitters, the Killer Frost drink.
- Like her mother, she's a widow.
- Caitlin is one of a few characters in the shared multiverse (including Tommy Merlyn and Thea Queen, Felicity Smoak, Leonard and Lisa Snart, Mon-El, Winn Schott, and Lex and Lena Luthor) to have a parent as a villain.
- In a deleted scene from "", Caitlin flashes back to when Barry was comatose and "Wells" told her he didn't want people to judge Caitlin based on the fact that she stayed at S.T.A.R. Labs after the particle accelerator explosion.
Behind the scenes
- In the DC comics, Caitlin Snow is known as the third iteration of the super-villain Killer Frost. In the current DC Rebirth line, unlike other incarnations of Killer Frost, Caitlin is a protagonist/anti-hero in the Arrowverse. Similarly, Caitlin in the Arrowverse started out as a villain during Killer Frost's emergence before becoming a hero.
- Furthermore, Caitlin is often seen wearing blue and/or white, foreshadowing/referencing her transformation.
- Caitlin's late Earth-2 counterpart fulfilled the traditional villainess Killer Frost role.
- Caitlin once mentioned that Ronnie Raymond referred to them as being like "fire and ice" as a couple, a reference to their future meta-human powers.
- Killer Frost once warned Norvock, "You're making me frosty. You wouldn't like me when I'm frosty." This is most likely a reference to a line said by comic-book character Bruce Banner, also known as the Hulk: "You're making me angry. You wouldn't like me when I'm angry."
- On Netflix, in certain episodes of The Flash, Caitlin's name is misspelled as "Caitlyn" in the subtitles.
- Caitlin had a different hairstyle in Season 2 because Danielle Panabaker fell and hit her head, so they gave her bangs to cover the scar.
|Other versions of Caitlin Snow|
|To see other versions of this character, click the Earth name below for that Earth's counterpart of Caitlin Snow.|
|Earth: 1 • 2 • Frost|