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- "You may be the fastest man alive, Allen. I'm the fastest mind."
- "So this is how we begin whatever twisted game you have planned."
"No, Mr. Allen. You've already lost and never even realized it."
- —Clifford DeVoe and Barry Allen[src]
The fourth season of premiered on October 10, 2017, on The CW and concluded on May 22, 2018. The season consisted of 23 episodes.
- Grant Gustin as Barry Allen/The Flash
- Candice Patton as Iris West-Allen
- Danielle Panabaker as Dr. Caitlin Snow/Killer Frost
- Carlos Valdes as Cisco Ramon/Vibe
- Keiynan Lonsdale as Wally West/Kid Flash
- Neil Sandilands as Professor Clifford DeVoe/The Thinker
- Tom Cavanagh as Dr. Harrison "Harry" Wells, Dr. Harrison Wolfgang Wells, H. Lothario Wells, Wells 2.0, Wells the Grey, Professor Eobard Thawne/Reverse-Flash, Sonny Wells, and H.P. Wells
- Jesse L. Martin as Detective Joe West
- Danielle Nicolet as District Attorney Cecile Horton
- Mark Sweatman as Matthew Norvock
- Kim Engelbrecht as Dr. Marlize DeVoe
- Dominic Burgess as Ramsey Deacon/Kilg%re
- Patrick Sabongui as Captain David Singh
- Jessica Camacho as Cynthia/Gypsy
- Donna Pescow as Dr. Sharon Finkel
- Richard Brooks as Warden Gregory Wolfe
- Sugar Lyn Beard as Becky Sharpe/Hazard and Professor Clifford DeVoe/The Thinker
- Danny Trejo as Josh/Breacher
- Hartley Sawyer as Ralph Dibny/Elongated Man and Professor Clifford DeVoe
- Katee Sackhoff as Leslie Jocoy/Amunet Black
- Chelsea Kurtz as Mina Chaytan/Black Bison
- Kendrick Sampson as Dominic Lanse/Brainstorm and Professor Clifford DeVoe/The Thinker
- Ryan Alexander McDonald as Neil Borman/Fallout
- Bill Goldberg as David Ratchet
- Jessica Parker Kennedy as Nora West-Allen/XS
- Derek Mears as Sylbert Rundine/Dwarfstar
- Paul McGillion as Earl Cox
- Miranda MacDougall as Izzy Bowin/The Fiddler and Professor Clifford DeVoe/The Thinker
- Leonardo Nam as Matthew Kim/Melting Point
- Bethany Brown as Janet Petty/Null
- Arturo del Puerto as Edwin Gauss/Folded Man and Professor Clifford DeVoe
|Running up against an evil time remnant version of yourself is something no one should ever have to do, but that’s exactly what faced Barry Allen (aka The Flash) as he fought to save the life of fiancée Iris West from the God of Speed known as Savitar.
Barry’s victory was short-lived, however, as an unbalanced Speed Force began to wreak havoc on Central City, forcing Barry to sacrifice himself for the greater good.
With The Fastest Man Alive now trapped inside an extra-dimensional energy, and unknown dangers lurking in the shadows, it will be up to Team Flash to free Barry from his own personal Hell.
|#||Episode name||Directed by||Story by||Teleplay by||Original airdate|
|1||""||Glen Winter||Andrew Kreisberg||Todd Helbing & Eric Wallace||October 10, 2017|
|With Barry in the speed force, Iris, Kid Flash, Joe and Vibe have taken over protecting Central City. However, when a powerful armored villain threatens to level the city if The Flash doesn't appear, Cisco makes a risky decision to break Barry out of the speed force. However, the Barry that comes out isn't the same Barry that went in.|
|2||""||Alexandra La Roche||Jonathan Butler & Gabriel Garza||October 17, 2017|
|Barry has his hands full when he takes on a dangerous meta who can control technology, while also confronting an obstacle in his personal life; the ramifications of abandoning Iris for six months to balance the Speed Force. Meanwhile, Gypsy breaches in for a hot date with Cisco, but she gets annoyed when his work keeps them apart.|
|3||""||Armen V. Kevorkian||Sam Chalsen & Judalina Neira||October 24, 2017|
|Barry and the team are hit by a string of bad luck and realize it is the handiwork of a new meta, Becky nicknamed Hazard, who has the ability to give others bad luck, while cashing in the benefits for herself. Meanwhile, Harry Wells returns to Earth-1 to give Wally a message from Jesse.|
|4||""||Tom Cavanagh||Sterling Gates & Thomas Pound||October 31, 2017|
|Cisco is shocked when Gypsy's father, Breacher, shows up on Earth-1. Breacher takes an immediate disliking to Cisco and decides to hunt him. Meanwhile, Barry runs into his old nemesis, Ralph Dibny.|
|5||""||Laura Belsey||Lauren Certo & Kristen Kim||November 7, 2017|
|Having received an ominous threat from her old boss, Amunet, Caitlin fears that her past time as Killer Frost may be back to haunt her. Felicity comes to Central City to help the girls celebrate Iris's bachelorette party, while Cisco, Joe and the guys take Barry out for a night on the town.|
|6||""||Brent Crowell||Jonathan Butler & Gabriel Garza||November 14, 2017|
|When collectors of Native American artifacts are attacked by a meta named Mina Chayton who can bring inanimate objects to life, Barry turns to a surprising ally for help. Determined to crack the identity of The Thinker, Harry enlists Cisco’s help to summon the ultimate think tank; "The Council of Wells", a roundtable of the brightest Harrison Wells’ from various Earths.|
|7||""||David McWhirter||Eric Wallace & Thomas Pound||November 21, 2017|
|Barry comes face to face with DeVoe. DeVoe's past is revealed through flashbacks. Meanwhile, Iris puts the final touches on the wedding, which is a week away.|
|8||""||Dermott Downs||Andrew Kreisberg & Marc Guggenheim||Todd Helbing||November 28, 2017|
|Barry and Iris's wedding brings the gang together, but things go awry when villains from Earth-X attack the ceremony. All of the superheroes band together with help from their super friends like Citizen Cold, The Ray, Felicity Smoak, Iris West and Alex Danvers to take on their most formidable villains yet. Earth's mightiest heroes - Green Arrow, Supergirl, The Flash and White Canary - lead their teams into battle to save the world.|
|9||""||Stefan Pleszczynski||Sam Chalsen & Judalina Neira||December 5, 2017|
|Amunet kidnaps Caitlin and puts meta-dampener handcuffs on her to keep her from turning into Killer Frost. Amunet tells Caitlin she needs her to perform a tricky medical task and if Caitlin fails, Amunet will kill her. Meanwhile, The Thinker traps The Flash in a speedster-proof prison. With the clock ticking, The Team doesn't have the time or resources to track both Caitlin and Barry so Iris is forced to choose who to save.|
|10||""||Philip Chipera||Lauren Certo & Kristen Kim||January 16, 2018|
|As Barry's trial for the murder of Clifford DeVoe begins, Iris and Joe must decide how far they are willing to go to keep Barry out of prison.|
|11||""||Alexandra La Roche||Sterling Gates & Thomas Pound||January 23, 2018|
|When a familiar villain returns to terrorize Central City, Ralph must rise up to defend the innocent while Barry is detained by his trial. Meanwhile, Barry searches for the strength to keep his optimism alive in the face of his new circumstances.|
|12||""||Chris Peppe||Sam Chalsen & Judalina Neira||January 30, 2018|
|A meta who can shrink anything he touches battles Team Flash. Cisco and Ralph get caught in his crossfire and are shrunk to miniature versions of themselves. Cecile realizes her pregnancy has caused her to have temporary powers and discovers she can hear other people's thoughts, which unnerves Joe. Meanwhile, Barry meets someone with a mysterious connection to Henry Allen.|
|13||""||Tara Nicole Weyr||Jonathan Butler & Gabriel Garza||February 6, 2018|
|After hearing that Amunet has struck a deal to buy all of the metahumans in Iron Heights, Barry must decide if he should expose his powers in order to save his cellmates. After a visit from an old friend, Ralph is reminded of his shady past and wonders if he's really a changed man.|
|14||""||Ralph Hemecker||Mike Alber & Gabe Snyder||February 27, 2018|
|Barry meets a powerful woman whose abilities could help him in his battle with DeVoe. Meanwhile, after learning that DeVoe is targeting everyone who was on the bus, Ralph decides he doesn't want to be a hero anymore, his only concern is staying alive. Harry offers to help Joe.|
|15||""||Gregory Smith||Todd Helbing & Sterling Gates||March 6, 2018|
|When a nuclear bomb detonates in downtown Central City, Barry, Jesse Quick and Jay Garrick slow down time by entering Flashtime. As everyone in the city is frozen, the three speedsters push themselves to the breaking point to save the city and everyone in it.|
|16||""||Harry Jierjian||Eric Wallace||March 13, 2018|
|Team Flash confronts a new bus meta, Matthew AKA Melting Point, with the ability to swap people's DNA. During a battle with Team Flash, Matthew transfers Barry's super speed to Iris. Now, with a new threat unleashed on Central City, Barry must act as the team leader while Iris takes on the mantle of superhero speedster in order to defeat their new foe.|
|17||""||Kevin Smith||Lauren Certo & Kristen Kim||April 10, 2018|
|Barry and Ralph take different approaches to finding the remaining bus metas before DeVoe gets to them. However, Ralph's cavalier attitude frustrates Barry and the two clash over what it means to be a hero. Meanwhile, Breacher returns to ask Cisco for a favor.|
|18||""||Hanelle Culpepper||Jonathan Butler & Gabriel Garza||April 17, 2018|
|When Barry and Team Flash find a way to enter the Thinker's lair, Ralph considers crossing a dangerous line to defeat DeVoe. Meanwhile, Joe is concerned by Harry’s recent behavior.|
|19||""||Rachel Talalay||Joshua V. Gilbert & Jeff Hersh||April 24, 2018|
|When Barry needs help transporting a dangerous meta, he calls on a new friend for help - Citizen Cold; Cisco becomes suspicious of Harry.|
|20||""||Rob J. Greenlea||Sterling Gates & Thomas Pound||May 1, 2018|
|Barry and Team Flash team up with Gypsy to try to thwart the Thinker's plan. Meanwhile, Cisco and Gypsy have a heart to heart talk about their relationship.|
|21||""||Kevin Mock||Judalina Neira & Lauren Certo||May 8, 2018|
|With DeVoe's Enlightenment device nearly complete, in order to disable it the Flash and his team must put their faith in an unlikely ally - Amunet Black. Meanwhile, Harry hits an all-time low when the "Council of Wells" kicks him out but then Cisco introduces him to the "Council of Harrisons".|
|22||""||Viet Nguyen||Sam Chalsen & Kristen Kim||May 15, 2018|
|When DeVoe assaults an A.R.G.U.S. facility to complete his Enlightenment Machine, Barry realizes the only way he can stop him is if he allows Cisco and Caitlin to accompany him into the facility. Still shaken by Ralph's death, Barry isn't sure he wants to risk any more of his friends' lives and considers taking on DeVoe solo.|
|23||""||David McWhirter||Todd Helbing & Eric Wallace||May 22, 2018|
|Team Flash gets help from a surprising ally in their battle against DeVoe.|
- This was the first season of :
- Where Rick Cosnett, Robbie Amell, Wentworth Miller, Dominic Purcell, Matt Letscher, Michelle Harrison, and John Wesley Shipp didn't reprise their roles as Eddie Thawne, Ronnie Raymond, Leonard Snart, Mick Rory, Eobard Thawne, Nora Allen, and Henry Allen.
- Where Grodd was not featured since his introduction in Season 1.
- Where King Shark was not featured since his introduction in Season 2.
- To not feature Jesse L. Martin as Joe West in every episode.
- To have a main antagonist that wasn't a speedster.
- This was the only season of to feature Neil Sandilands as a series regular.
- This is the last season of to have 23 episodes. The next season would have fewer episodes.
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