Caitlin Snow


 * For other uses of "Killer Frost", see Killer Frost (disambiguation).

Dr. Caitlin "Cait" Snow is a former scientist at Mercury Labs and a bio-engineer at S.T.A.R. 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 his true identity as Eobard Thawne, and provides medical support for the team. Caitlin is also the wife of the late Ronnie Raymond, and is close friends with Cisco, Barry and Felicity Smoak. She is also the former lover of "Jay Garrick", before discovering his true identity as Hunter Zolomon and the former girlfriend of Julian Albert.

In the Flashpoint timeline, Caitlin is not a scientist but is 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 also seemingly from changing time again she is also a meta-human with abilities similar to her Earth Two doppelgänger, who she is afraid of becoming like. However it's also implied that she could have been affected prior to Flashpoint. After being taken over by her rising anger while using her meta-human powers, losing control of her emotions, she 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.

Early life
From a young age Caitlin idolized her parents who were both doctors and was inspired to follow in their footsteps. Growing up Caitlin practiced the Hippocratic oath and was obsessed with it. She grew to value life so much she wouldn't even let anyone step on a bug if she could help it. From a young age Caitlin was very close with her father. One Christmas they sat and watched old movies together as it snowed for hours without end outside. However Caitlin's father suffered from multiple sclerosis. Her mother Carla Tannhauser tried to save him as he fought it for years but he eventually died, much to Caitlin's heartache. Following her father's death Carla began focusing only on her work as a way to cope with losing her husband, but her neglect of Caitlin left them estranged for several years.

In high school Caitlin was bullied by Lexi LaRoche who put chewed bubble gum in her hair. In adult years Caitlin became a trained neurosurgeon but was still estranged from her mother. Despite being estranged Carla still offered Caitlin a position at Tannhauser Industries but Caitlin wanted to make a name for herself and declined. Some time before 2011 Caitlin was hired at S.T.A.R. Labs by Dr. "Harrison Wells". Sometime after this she met Ronnie Raymond a structural engineer who in contrast to Caitlin's guarded outlook was more outgoing. Caitlin would later describe them as being "Fire and Ice". Despite being very different the two fell deeply in love and started dating. Though she enjoyed working at S.T.A.R. Labs she, like most employees, was often irritated by Dr. Wells' protege 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 and he would consider her and Ronnie family, as he was estranged from his own and looked up to the couple. Eventually Ronnie proposed to Caitlin and she accepted. However she apparently never told her mother as she wouldn't even be aware Ronnie existed until over 1 year after his actual death.

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 fiancé, Ronnie, were discussing their honeymoon when they were alerted of the impending switching on. After he switched it on, Dr. Harrison Wells went to make a toast, but it was 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 in to lock-down, locking him inside the core chamber. Caitlin and Ronnie talked, but before they could continue, Ronnie's connection was lost, apparently being 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. Sometime following his move, Cisco, along with Caitlin, 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 the two of them 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 to Mirakuru that would be used to cure the Mirakuru soldiers during Slade's seize of the city and 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 lab as quickly as possible, and explained to Barry what had happened, introducing he 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 collided 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 in to 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 to 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 in to 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 in to 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 in to the open, Caitlin reminded him not to breath 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 to 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 mor 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, every one 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 an whisky 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. She was later rescued by Cisco and Joe West.

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 it's 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.

Enter Zoom
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 doppelganger. 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 a 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 doppelganger 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 after becoming the Flash, and Hunter's cells were no longer compatible.

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 it's rings when it fell apart. As Caitlin and Jay tried to repair it Joe told them of a metahuman 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 she discovered a flaw in it's 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 though 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 sleep it off.

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 were 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 doppelganger. 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-2 to beat Zoom.

While enjoying a night out at a dance club Caitlin and Cisco danced while Barry, Iris, Wally and Jesse watched but the club was attacked by another speedster, Trajectory, and Caitlin suspected the speedster was using Velocity-9 and told Barry about it. However Barry was furious to learn Caitlin had the means to increasing 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 but when she and Joe questioned her about the research Caitlin gave her, she revealed she destroyed it after helping her and Eliza checked out. However the team was attacked by Trajectory who locked Flash in the pipeline and revealed she was indeed Eliza, demanding more Velocity-9 and threatening to kill Jesse. After succeeding Trajectory injected Jesse with Velocity-9 and escaped and 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 shockingly confirmed that Jay is Zoom.

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 doppelganger'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 Two 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. Reluctantl,y 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 discover 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 One. 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 One. Zoom then took him with her back to Earth One.

Returning to Earth One, Caitlin became a witness to Zoom's ruthless conquest of 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 Two. 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.

Return of Killer Frost
Whether as the result of Flashpoint or not, Caitlin developed 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 solid 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 he 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 web cam 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 he to reveal the truth about her powers to the team.

Caitlin was forced to use 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, Killer Frost turned against Barry in anger, and despite him saving her from the CCPD, 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 in 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 who yelled at him, blaming Barry for everything bad that happened to the team after his "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 put power dampeners on herself she hug him with Barry said "that's okay i got you", assisting the team in returning Wally to normal (albeit now with Super-Speed).

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 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 raincloud above West House into a cloud of white snow.

Attack on S.T.A.R Labs
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.Soon after, this led to Caitlin supervising her own surgery. Initially, it went well and she fell asleep. Later however, her heart rate spiked, causing her to die. Confused about what to do, Julian considered whether he should respect her wishes, that she'd rather die than become Killer Frost, or to tear off the power-dampening pendant to possibly bring her back. Julian ultimately decided to tear the pendant off, which resulted in Caitlin's heart being revived and her heart rate steady. 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.

Alliance with Savitar
Soon after her escape from S.T.A.R Labs, Caitlin is wandering around in the snow and finds Savitar. She then asks if Savitar wants to cure her, to bring Caitlin Snow back, to which he replies that he wants the opposite. Caitlin asks why she should trust him and Savitar removes his armor, which causes her to state she'll do anything he wants.

Possible future
According to Craig, a member of Savitar's cult, Caitlin will be described as being "glorious and powerful", and Savitar will have "special plans" for her.

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 reads "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 remains the same. Barry laters 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.

When Barry visited a possible future, in the year 2024, it is revealed that Caitlin allied herself with Savitar. Moreover, during the aforementioned 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 the Pipeline, and still refuses to divulge the identity of Savitar, with Julian as her caretaker.

As a civilian
Caitlin is very intelligent and passionate about her work as a bio-engineer and scientist, even keeping a blood collection kit in her purse. She is generally a very compassionate and caring woman. She loved her fiancé Ronnie Raymond very much, he knew how to make her laugh and was devastated by his death which sent her into a state of depression for almost a year, because 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.

After her imprisonment with Hunter, it seems that Caitlin is 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 cryokenetic 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.

As Killer Frost
Worrying about her newfound, 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 Snow never to come back. She allies herself with Savitar after he reveals himself to her.

Powers



 * Meta-human physiology: After Caitlin was caught in the particle accelerator's explosion's shockwave, this also altered her DNA and supercharged her cells, augmenting her physiology to properly access her powers.
 * Energy absorption/Cryokinesis: The nature behind Caitlin's powers is to absorb all existing heat around her, thereby reducing the temperature around her, to which she is able to freeze objects to temperatures well below negative 370 degrees. At tell-tale sign of her accessing her powers is producing icy mist from both of her hands. Caitlin can also create solid structures made of ice with ease, making an icicle that could kill Barry with seemingly no effort do to the freezing temperatures impeding his healing powers. Caitlin also demonstrated that she could change the weather so that it snow for her friends when they were going through a difficult time. She can also counter Clive Yorkin's decompossing powers.
 * Accelerated healing factor: While accessing her powers, Caitlin's metabolic rate is augmented to offset cold tissue destruction, thereby allowing her endure more grievous injuries and likewise heal much faster than a normal human. In fact, her healing speed may exceed Barry Allen's, as her relatively fresh-stitched impalement wound healed in a mere seconds after she regained access of her powers.
 * Cold immunity: Possibly as an added benefit to her powers, Caitlin also exhibits a high resistance to frigid temperatures. She is shown to be able to hold the ice constructs she manifests with little trouble.
 * Freezing breath: Caitlin is able to create a fog with her breath. She used this ability when she was trying to know the whereabouts of Alchemy by threatening one of his followers in an interrogation room at CCPD and created a fog in the room in order to escape.

Abilities

 * Computer specialist: As an member of S.T.A.R. Labs, Caitlin is shown to have some technological skills of note, albeit not her main area of expertise as was evident in her ability to reprogram S.T.A.R. Labs satellite to track meteorological abnormalities over Central City, so they could find the location of Clyde Mardon.
 * Expert medic: Caitlin is shown to be an expert in medical care, as seen when she was able to cure Barry Allen after he was poisoned by Kyle Nimbus, and later, when she was able to patch-up the former when he was seriously injured by Tony Woodward, Caitlin was also able to patch-up "Harrison Wells" after he was brutally beaten up by his Reverse-Flash speed mirage.
 * Genius-level intellect: Caitlin is very intelligent, as evidenced by the crucial role she plays in Team Flash, she along with Cisco Ramon were able to create a cure for Mirakuru.
 * High pain tolerance: Caitlin is shown to have a remarkable level of endurance. Despite the grievous injuries she gained from Abra Kadabra, she was able to maintain consciousness through the surgery to remove the shrapnel in her body, all while instructing Julian.
 * Trained neurosurgeon: Caitlin once mentioned that she knows how to perform a lobotomy, a procedure that requires both training and skill in the field of neurosurgery.

Weaknesses

 * Emotional instability/Borderline personality disorder: As a result of Caitlin's changing biology having physiological affects, making her cruel and sadistic, very emotionally detached and little regard for human life, while she struggles to retain her compassion and sanity, she has developed a form of dissociate identity disorder which is triggered the more she uses her powers and subsequently when she is angered. It is difficult to calm her down when her Killer Frost persona takes over, as her mother was just barely able to stop her from killing her research assistant who attempted to kidnap Caitlin for his experiments. She was also willing to attack Barry and Cisco, but when Barry dared Killer Frost to kill him as he stood unarmed, she was unable to kill him causing her to revert back to her normal persona. The change can be seen as the case of Caitlin losing and regaining the sense of self-control over her emotions, the super-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 developing (like it happened in Frankie Kane's case).
 * 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 Cait accidentally freezing her laptop. Recently, Caitlin has seemingly begun to use her powers (in small doses) with no adverse affect, as shown at Christmas of 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 it is still hinted that if she uses these powers too often her altered appearance will eventually become irreversible.

Former equipment

 * Power-dampening cuffs: After her powers began manifesting, due to her unstable control over them, Caitlin initially wore a pair of Cisco's power-dampening cuffs on her wrists as a means to help keep her powers in check. However, she abandoned 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 said made her "feel like a human tablet".
 * Solar power collection pendant: Julian made Caitlin a pendant designed to dampen her powers, as well as to collect solar energy in order to help charge it whenever she went outside, so that it continues to work without constant recharging. However, upon her temporary death, Julian removed it.

The Flash
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Season 3
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Novels

 * The Flash: The Haunting of Barry Allen

Trivia

 * According to Caitlin herself, she practiced the Hippocratic Oath repeatedly as a child.
 * In an erased timeline Caitlin is the first person to discover that Dr. Wells isn't paralyzed after she discovers his wheelchair vacant while they are at CC Jitters. However, due to Barry changing the timeline Caitlin remains unaware of this discovery, though she did learn 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, due to Barry Allen changing the time continuum this disaster never occurs.
 * Although Killer Frost is a meta-human in Earth Two, Caitlin has explicitly stated that she has carried out tests which confirm that she does not have the meta-human gene, the first hint at a more subtle difference between the two worlds rather than the more explicit differences of certain characters having made different choices.
 * It should be noted that Cisco, who was presumably tested after the accelerator explosion, wasn't aware he was a meta-human for almost two years, until his death in an erased timeline triggered this powers. It is possible that Caitlin could in fact be a meta-human with the same powers as Earth-2 Caitlin, but never triggered the gene.
 * After the Flashpoint changes to the timeline, Caitlin is seen expressing cryokinetic abilities similar to her Earth Two alternate Killer Frost, which she is hid from the others. Unlike her Earth-2 doppleganger, her eyes turn whitish-blue when accessing powers.
 * The major difference between the two is that Caitlin is kind and compassionate, fearing losing that side of herself; Killer Frost from Earth Two is cruel and sadistic.
 * Apparently Caitlin Snow doesn't exist on Supergirl's Earth. However as shown by Jay Garrick being Henry Allen from Earth Three, same versions of people do not necessarily have the same name.
 * While Caitlin was revealed to have powers in the end of "Paradox", some of the struggles she's been going through are similar to Siobhan Smythe/Silver Banshee when it comes to being scared having powers, the stress they had and have to go through before and after they manifest, and the trauma brought upon them by friends like Cisco and Winn not being trusted on keeping the most personal secrets from others over what the know is right and wrong.
 * The only difference between the two friends of the hackers turning to the darkside is that Siobhan was able to maintain her mental stability by maintaining further sense of optimism while Caitlin can not because she fears becoming her doppelganger  and because of the hassle Zoom caused Barry on his last rebound with his archenemy from Earth Two that she didn't want to make problems worse for him.
 * Though not admitting it, some of Caitlin's actions have made it clear that she is attracted to Barry. While at the dive bar with Barry where the two look for new love interests, she gets drunk and drops several hints of her attraction to him, even singing "Summer Lovin" with him and flirtatiously joking about it when she realizes afterwards that he's actually a very good singer. She later, while still drunk, asks him to help her change out out of her clothes to her night garb and then asks him to tuck her in. When Hannibal Bates disguises himself as Barry and kisses her to distract her from working on serum to use against Hannibal, she is surprised initially and stops him but when he kisses her again, she passionately begins to make out with "Barry" until Iris arrives, causing the two to awkwardly pretend it never happened. When Hannibal disguises himself as Caitlin while trapped in the pipeline to attempt to flirt his way out by calling Barry "handsome" he smirks and looks over to Caitlin only for her to awkwardly fakeingly deny that she would say that.

Behind the scenes

 * In the DC comics, Caitlin Snow is known as the third iteration of the super-villain Killer Frost. In the first season finale there is a brief glimpse of Caitlin as Killer Frost when Barry travels through time.
 * Caitlin says in that Ronnie referred to them as a couple as "fire and ice", a reference to their respective DC comic identities.
 * Furthermore, Caitlin is often seen wearing blue, another possible reference to her super-villain alter-ego in the DC comics.
 * In the DC comics, unlike other incarnations of Killer Frost, Caitlin is a protagonist/anti-hero rather than a super-villain. However, in the Arrowverse, Caitlin's Earth-2 counterpart fulfills the traditional Killer Frost role.
 * In season 3's, executive producer Todd Helbing dubs Caitlin's metamorphosis as "Caitlin Frost" demonstrating that it was one of the slow progressive steps in her fulfilling her eventual destiny.
 * In season 4, it's unknown if Caitlin will return or she will remain Killer Frost.