Barry suddenly gains the power of speed thinking. He attempts to use this power to save Iris, but at the cost of nearly losing his morality.
Tropes:
- All for Nothing: After Barry realizes he's endangered his friends and wife by relying on his speed thinking, he destroys the Artificial Speed Force. Thus rendering Nash and the other Wellses' sacrifice in vain.
- Back from the Dead: The Stinger shows the original Earth-1 Harrison Wells coming back to life.
- Batman Gambit: The whole super-speed fight is just a ploy for Barry to take out all of Team Flash in one go.
- Behind the Black: Inverted. Cisco is somehow able to see the computer screen that is clearly facing the camera and away from him.
- Celebrity Paradox: Cisco calls the TV host where Eva appears "Rachel Maddow 2.0". Rachel Maddow voices Vesper Fairchild over on Batwoman (2019).
- Chekhov's Gun: The quantum ball, a device developed by Cisco, which amplifies kinetic energy, making it fire in unpredictable directions. Barry actually uses it to incapacitate his team, being able to precisely predict its movements.
- Cliffhanger: A particularly nasty one. Cisco, Frost, and Allegra have been wounded fighting Barry, Barry destroys the Artificial Speed Force and seems to have lost his speed again, Iris is back from the Mirrorverse but has gone into a coma, Singh and Kamila are still stuck in the Mirrorverse and in danger of dying, and Eva is starting to replace everyone in Central City with mirror duplicates.
- Continuity Porn: The memorial for Team Flash’s fallen friends and allies features a number of mementos from across the series.
- Harry Wells’s glasses.
- H.R. Wells’s drumsticks.
- Nash Wells’s backpack.
- Leonard Snart’s goggles.
- Nora West-Allen’s XS jacket.
- Jesse Quick’s jacket.
- Ronnie Raymond’s jacket and Firestorm matrix.
- Oliver Queen’s original mask.
- Creepy Monotone: Barry when under the influence of the Artificial Speed Force.
- Curb-Stomp Battle: Barry is an experienced speedster who's been fighting other, even more experienced speedsters (Thawne, Zoom, Savitar) for years. Frost is, while an experienced combatant, brand new to the super speed business. There was only one way that fight was going to end.
- Curb Stomp Cushion: While Barry ends up whopping Team Flash's asses in his sociopathic state, the team is able to get in a few good blows.
- Didn't See That Coming: Just like DeVoe before him, Barry's coldly logical thinking makes him unable to correctly predict the emotional responses of his friends and loved ones, incorrectly believing that Iris would agree with leaving Singh and Kamila behind in the Mirrorverse.
- Due to the Dead: During the eulogy to all the Wells's, it’s revealed that S.T.A.R. Labs has a room filled with mementos of the friends and allies they’ve lost over the course of the series, with Cisco noting that their names have been nano-engraved into the wall so they will remain no matter what changes happen to the timeline. See Continuity Porn for more information.
- Easy Come, Easy Go: Just one episode after regaining his speed, Barry, after realizing how dangerous the speed thinking it gave him is, destroys the Artificial Speed Force, putting him back to square one with his speed in danger of running out.
- Evil Cannot Comprehend Good: Cisco is baffled that Barry would actually predict him and all of their friends voting for saving Singh and Kamilla and leaving Iris behind. Barry is also left confused when Iris resists being rescued to save Singh's and Kamilla's lives.
- Godzilla Threshold: In order to detain Barry once he starts becoming sociopathic, Frost injects herself with the same Velocity serum Zoom used, temporarily giving herself super speed.
- Heel Realization: At the end of the episode, Barry realizes that his speed thinking has caused him to become emotionless and hurt his friends.
- He's Back!: Frost returns this episode, with her powers and condition finally fully restored.
- Internal Reveal: Barry deduces Eva's status as a mirror duplicate and exposes it to the public.
- Love Is a Weakness: Barry muses on this idea after considering how Eva used his heart to manipulate him and how so many other villains have done the same before. Given his previous beliefs that love is more important than anything else, this is the first hint that something is wrong. It only gets worse the more he uses his Speed Thinking.
- Madness Mantra: A late scene has Eva repeatedly muttering, "This isn't my world." She then concludes, "But it can be."
- Mirror Character: Barry gains the power of Speed-Thinking, the same power DeVoe used, and like him, starts to become devoid of emotion, neglecting his loved ones, making sociopathic decisions convinced they'll have the best results, and losing the ability to even understand people's feelings or virtues. But unlike DeVoe, Barry never quite loses sight of his original mission and loves his friends and family enough to snap out of it.
- Mistreatment-Induced Betrayal: Millie Rawlins apparently leaves her boss after the truth about Eva comes out, as was indicated earlier by her warning Eva to not repeat her late husband's mistakes and keep secrets from her employees.
- My God, What Have I Done?: Barry when he comes to his senses after Iris collapses in front of him and realizes that his efforts to stop Eva have only hurt his friends and wife.
- Nice Job Breaking It, Hero: Barry exposes Eva as a mirror duplicate in the middle of a live television broadcast with Arielle Atkins, causing Eva to abandon her original plans and start replacing everyone in Central City with mirror duplicates.
- Not Himself: Barry.
- Not So Stoic: Even before his My God, What Have I Done? moment, Gideon noticed Barry was distressed when he predicted that the rest of Team Flash would vote to save Kamilla and Singh over Iris, and despite claiming that he's only choosing Iris out of logic, it's her collapsing upon leaving the Mirrorverse that snaps Barry out of his emotionless state.
- Relative Button: Barry calling Kamilla and Singh "expendable" is the last straw for Cisco and he signals the team to attack Barry.
- Rogue Protagonist: Barry has become cold and calculating, forcing the rest of Team Flash to try and stop him.
- Rule of Cool: There's no way that even Velocity-X should have allowed Frost to keep up with Barry, given how much faster he is than when he fought Zoom, and Frost should not have been so good with her speed the first time out. However, both of those things are ignored so that the viewers can be treated to a glorious super-speed battle between Frost and Flash.
- Given how Barry stands around waiting for Frost to throw her lightning-infused ice blast at him, it's possible he deliberately slowed himself down as part of his ploy to take out the rest of the team.
- Sadistic Choice: Due to a combination of the amount of time spent in the Mirrorverse and amount of photons available, the portal was able to bring back only Iris or Kamila and Singh. Barry predicts that the others would choose to save Kamila and Singh, but Cisco calls him out on it, saying he'd never make that kind of choice and would find a way to save all of them.
- Sanity Slippage: Barry exposing her to the world destroys what little sanity Eva had left.
- Sociopathic Hero: Barry becomes one due to the Artificial Speed Force messing with his head.
- The Spock: Subverted. It appears that Barry has become this, but what's happening in his head is both more insidious and dangerous than simply "intelligence equals emotionlessness".
- Spotting the Thread: Thanks to his super-thinking and Carver's dying words, Barry figures out that Eva is a mirror duplicate.
- The Stoic: The speed thinking causes Barry to become a cold, emotionless robot.
- To Be Continued: The third episode in the series to end with this.
- Took a Level in Jerkass: The influence of the Artificial Speed Force causes Barry to disregard people's feelings, including turning against his friends to save Iris even if it means leaving Kamilla and Singh to die.
- The Unreveal: Whatever Eva's original plans were have gone out the window now that Barry has exposed her secret to the public. Instead, she's decided to replace all of Central City with mirror duplicates.
- Villainous Breakdown: Eva goes berserk once the footage of the original Eva's death from the last episode is leaked by Barry and she exposes herself as a mirror copy, then she decides to replace everyone in Central City with duplicates.
- Wham Shot: During The Stinger, after Barry destroys the Artificial Speed Force, we see Earth-1 Harrison Wells materializing from the spot he was buried after Eobard Thawne stole his body roughly twenty years ago.
- What the Hell, Hero?: Naturally, Barry's friends give him numerous of these throughout the episode.
