Plot

With The Flash still reeling from everything that just happened, the rest of the team rallies to support him when he needs it the most.

It's the final battle between the Speedsters and the Negative Forces, while Iris gains an unexpected Ally in her battle to fight the time sickness invading her body. The Negative Forces reveal their master plan and choose a new avatar., who promises doom to Flash.—Gislef

Fast Track screams as Thawne takes over Eobard's body, and become Reverse-Flash. When Barry wonders how his nemesis can be alive. Reverse-Flash says that the Negative Forces brought him back because they were too weak without him. Reverse-Flash says that killing Nora led to the birth of Flash, and killing Iris led to the rebirth of him, and Nora and Iris ere good for something.. Barry blasts Reverse-Flash with lightning, and Impulse and XS in and tell their father that killing Reverse-Flash isn't worth it., and will make him just as bad as Reverse-Flash is. When Barry finally relents, Reverse-Flash tells Barry that if Barry doesn't kill him, he'll come after Barry's children X and Impulse points out that they haven't been erase from the timeline, which means Iris isn't dead yet/ Reverse-Flash smirks and then disappears in a burst of energy.

At Meena's company, Cecile senses that Barry and Meena are both hurting. Team Flash figure they have to recover Iris, then take down the Forces. Nora figures the Forces won't come back because they already got what they came for. Barry comes over and says he has to find a way into the Negative Speed Force, He figures they don't have a choice no matter how insane the idea is, When Cecile advises, Barry snaps at her saying that Reverse-Flash killed Iris. Nora says that she and Bart need to talk to their father privately. The team gives the trio privacy, Once they're alone, Nora tells Barry to let her and Bart handle it. Barry says that they didn't see Iris dies in his arms, and suggests Iris might have been erased from the timeline but the changes haven't caught up to them. Bart figures that Barry still wants to kill Thawne.

Iris appears in a white version of the bar. Damien greets her, and says that they have a lot to discuss.

The team returns and Barry says that going into the Negative Speed Force is the only way, using a tachyon generator. Meena needs a source of negative lightning like her, and Barry tells Chester to get started making a device. Cecile empathically senses that Barry wants revenge, and Barry says that he knows Iris isn't alive. She hears someone calling her name, and she picks up desperation. The positive Psych appears to Cecile and says that she's the only one who can help them, then flickers out of sigh. She figures Psych wants her to bring back the Positive Forces.

Thawne appears in a red tinted copy of the loft, in the timeline where he and Iris were married. The Negative Forces step out and say they wanted Thawne to feel at home. Thawne wonders why he's there, and the Forces say that the Negative Speed Force chose Thawne because of his hate. Eobard didn't hate, and that's why he had to go. Thawne says that he's not going to play their game, and Deon freezes Thawne in time. They say that they're going to transform him, and Thawne's eyes glow.

Damien figures that Iris had just figured out that the Forces used her body as an incubator to recreate Thawne. She's inside Damien's Time Stone, and can't feel her connection to Barry. "Damien" explains that he's a remnant of the original Damien's consciousness, trapped inside the Stone. She isn't supposed to be dead, unlike him. The Forces annihilated her body, but the Stone spared her consciousness because it sensed she still has something important to do. Damien asks Iris if she's up to it.

At STAR Labs, Chester rigs three harness, and Barry, Bart, and Nora put them on. The harnesses light up and the speedsters moan in pain. Barry tells Chester not to stop, but he shuts it down anyway, Barry says that they need another way, and Meena figures Eobard would know another way, but he's gone because of her and the BLOC machine. Meena speeds off to her lab and prepares to destroy BLOC. Barry stops her and says that Thawne was the one who destroyed her life. She relents and says there's nothing they can do about it. Barry has an idea and says that they need her work so she can get charged and then share her speed with him.

Once Meena enters BLOC and charges up, and makes him promise to kill Thawne, and he does. They join hands and Meena transfers her speed into him.

Joe is at home begging Iris to come home to him. Jay and Joan appear, and they say that they have been following Iris' particle stream across time, and the trail led them there. Jay finds a Time Stone in a cabinet, and Joe says that Damien gave it to him and said Joe might need it some day. The Stone is glowing with the energy of Iris' consciousness, and Joan figures the consciousness has ended up inside the Stone. Joe wonders how they get his daughter's consciousness out of the Stone.

Allegra, Rosalind, Mona, and Cecile go to the Citizen office. Cecile tells Rosalind and Mona to concentrate. When they do, Psych appears and says that Iris' time sickness spread to the Positive Forces, and they tethered themselves to persons. He tethered himself to Cecile, opening up her consciousness and expanding her powers. Cecile now has the strength to bring back the Positive Forces back, and she agrees.

When Chester detects the energy surge at Fast Track Labs, Nora and Bart take him there and they see Meena transferring energy into Barry. Barry disappears and appears in Thawne's apartment, and Thawne is still frozen with his eyes glowing. The Negative Forces appear and tell Barry that Thawne is going through some changes, helping him reach his full potential. Deon explains that Barry came at them first when he cut off Thawne from the Negative Speed Force, and they're ready now. Barry tipped the scales, and they're putting things back to normal and then some. They didn't know how to upset the cosmic balance until Barry showed them it could be done. Deon sends Barry back to reality, and he tells the others that the Forces are transforming Thawne.

Chester picks up a burst of negative tachyons over downtown. A black-suited Thawne appears in downtown, glowing with energy. People run, and Thawne tells them there's no point in running because they're all going to die. With that, he starts blasting people down with his lightning. The team watch on the news cameras, and Barry realizes that Thawne has the power of all the Negative Forces. He figures the Forces did so to tip the balance of power in their favor, and turn the entire world into a living hell.

In the Stone, Iris figures that her unfinished business is Barry. Damien tells her that she has to figure a way out and says that she's never died when she should have, because she's a survivor and always will be. Iris realizes that she hasn't reached her limit, and Damien tells her that the connection between her and Barry is still there even if she can't feel it. Iris says that she's going to reignite the connection, and glows with energy. She disappears as Damien smiles in satisfaction.

Thawne continues blasting people down. Flash and the other three speedsters whisk everyone away, and then confront Thawne and warn him that he's outnumbered four to one. They run around him, and then simultaneously unleash lightning at Thawne, bringing him down. Thawne becomes Impulse, and the others Thawne realize he substituted Impulse in his place. Thawne appears behind them, and sends Fast Trask and XS back a billion years in time. Flash run off and Thawne follows him.

Psych tells Cecile that they only have one chance, and then tells Cecile to put on his mask. She does, and the power she has and absorbed were enhanced by her ability to care about people, which Psych lacks. He explains that the mask will absorb her psychic power and give them to him. Allegra hold Rosalinda and Mona off from taking the mask, and Cecile put on the mask and screams in pain. The mask vanishes and Psych vanishes.

Thawne stops to kill more people. He's moving so fast that Flash appears to be standing still, and destroys an approaching police car with his lightning. Thawne laughs in triumph, and tells Flash that he could have stopped him by killing him when he had a chance.

When Thawne throws a lightning bolt at Barry, it stops in midflight. The Positive Forces appear and say they're doing it, and they have more power than Thawne. The Forces join hands and transform into energy, then flow into Flash's body. He tells Thawne that it's the end, and says that they're equals. Thawne insists that he's better than Flash and extends a tendril of energy. Flash grabs it and throws Thawne into a car, then speeds after Thawne as the latter runs away and beats him.

At the West house, a temporal disruption comes from within the Stone. Iris appears, and she and her father hug. She says that Damien showed her the way back, and the house shakes. Joe turns on the news, and they watch a broadcast of how the fight between the two speedsters is turning Central City into a warzone. Joe and Jay realize that Barry is doing more harm than good,, and Barry has started Armageddon. Iris has Jays take her downtown.

Thawne and Flash grapple, and Thawne manages to throw Flash away. Iris and Jay arrive, and Iris runs over to hug her husband and tells him that he has to stop because the city can't take any more fighting. Thawne says that they won't stop until one of them is dead, and it's time to tip the scales. Flash tells Jay to get Iris to safety, then tells Thawne that he's tired of fighting him. The speedster sits down, and Thawne blasts him. His energy goes through Flash, and Thawne figures he needs more power. Flash warns him that he won't survive, but Thawne doesn't believe him. A wave of energy sweeps through the city, destroying everything in its path.

Everything freezes in time, then time flows backward Thawne mutters that it isn't supposed to end like it is, then the energy consumes him. Barry's eye glow with the energy of all the Forces, then he stands up, snaps his fingers, then brings Meena and children back. They look up and see the energy of the Forces in the sky, and Flash says that it's the universe resetting itself.

Later at the loft, Joan confirms that there's no sign of Force particles in Flash's body, and Iris time sickness is gone. Gideon confirms that there's no sign of Thawne in the timeline, and they figure it's really over. Barry apologizes to his children about how he acted earlier, and they tell him that he did the right thing in the end. The four of them go back to 2049, and Meena says that BLOC is no longer working. Barry says that the Negative Speed Force used her to pick its avatars. Iris gives Meena Eobard's yellow tie they found at STAR Labs. She thanks them, offers Team Flash her technical expertise if they need it, and goes.

Chester and Allegra scan Cecile and confirms she's back to her normal level of empathy, and Mona and Rosalind have their powers back. Mona is back in prison, and they share a toast to Team Flash. Cecile displays telekinesis by accident,

The next day, Iris brings Tinya to her office at CCC. Flash brings Renee in to reunite her with her daughter, and he explains that when Iris was cured of her time sickness, it cured the Still Force and Renee showed up in Coast City.

In Caitlin's apartment, the chamber malfunctions, and the alarms wake Make up. He opens the chamber and a woman inside of it says that he's a friend... she thinks.

In the loft, Barry and Iris lay on the sofa and Barry tells his wife that he never wants to let her go. He says that he couldn't feel their connection, and Iris says that she felt the same in the Stone but he's her lightning rod. They kiss, and Barry thanks Iris for remind him Flash has limits. She says that the Negative speed Force will need to find a new avatar, and Barry figures when the day comes, they'll be ready for it.

In 2049, a crystal in a lab glows with negative speed force energy.