The Waverider returns to Central City, after dropping Thea off in Star City. Everyone discusses what the prisoners went through and how the Dominators are probably targeting metahumans. Ollie thinks they should abduct a Dominator to interrogate. Nate suggests going back to their first attack, in 1951, to find one. Cisco offers to come too, excited about time travel. Felicity volunteers as well. Meanwhile, the new President calls.
Ollie asks Supergirl to step back from everything. Things are too crazy and he needs some normalcy back. Supergirl is not pleased.
On the Waverider, Cisco and Felicity geek out, overwhelming Nate with their science talk.
Caitlin goes to see Martin, who is working at S.T.A.R. Labs. She has brought Martin’s daughter, who has a PhD in nanotechnology. Martin covers, but is clearly uncomfortable.
The Waverider lands in Redmond, Oregon. 1951. Along with Nate, Felicity, and Cisco is Mick and Amaya. Felicity is sick from time travel. Mick orders Cisco to stay on the ship with Felicity, something Cisco is not happy about.
Mick teases Nate over his Steel costume. They find the dominators fighting soldiers, and look for an opening to grab one.
Cisco is bored. Felicity accuses Cisco of wanting to come on this mission to get away from Barry. They used to dream about things like having powers and being heroes, but now that it’s reality, it’s hard. Felicity points out the importance of relying on friends.
The fight is over, and the Dominators drag away their prisoners. Mick sees one separate from the others, he and Steel knock it out.
Stein’s daughter tries to work with her father, but he is clearly distracted. Caitlin talks to Martin alone, and he admits that his daughter is an aberration, one he created. Once they defeat the Dominators, he plans on erasing her from history.
Men in suits, including one with glasses, tranquilize Nate, Mick, and Amaya. They take them, and the captured alien as well.
Cisco and Felicity want to save the others. They find weapons.
Mick, Amaya, and Nate are locked in a room. The drugs in their systems are preventing Amaya and Nate from using their powers. In the same room is the Dominator. And it is not happy.
In Central City, 2016, The Green Arrow, The Flash, White Canary, and The Atom wait for the President. Instead, they are surrounded by men in suits with weapons. Including the old man Lyla spoke to on The Flash. He’s the same man who captured the Legends in 1951.
Nate starts to question the Dominator. The Dominators try to determine how big a threat metas are. Their captors remove the Dominator from the room.
The Flash stops the guards from shooting them and the group fights until Glasses is the only man in a suit still standing. He calls the aliens xenomorphs and explains they consider Metahumans to be a huge future threat.
Cisco and Felicity break into the cell, freeing the Legends. They hear the Dominator being tortured and Nate insists they save it, to show that humans and metas can be good. They save the alien, who is being experimented on. They give it the ship that Ollie and the others used to escape in on Arrow. Cisco stole a transponder from the alien ship, so they can communicate with the Dominator. They return to 2016.
Green Arrow, The Flash, The Atom, and White Canary continue to question Glasses, who knows that The Flash is Barry Allen. By creating Flashpoint, Barry broke the truce humans have had with the aliens since 1951. They will leave earth, if Barry is sacrificed.
On the Waverider, they communicate with the same alien, now in 2016. It tells them that they will be spared for saving its life. But not Barry.
The Dominators have a weapon to kill all metahumans, and millions of regular humans will be killed by it as well. Sara wants to make contact, but the Dominator no longer responds to the transponder.
Cisco tells Nate that he can vibe them to the ship. But if he misses, they’ll be in space. They try anyway, and find the Dominator they saved on his ship. They can’t convince it to stop. Back on earth, Cisco realizes he also changed time. By saving this alien in the past, they increased the threat to earth. The same mistake Barry made.
Stein’s daughter loses her temper when she can’t figure out the next move and storms out. Caitlin tells Martin to talk to her, she can’t work because she’s wondering why her Dad is so distant. They can’t save the world unless he fixes their relationship.
Martin catches up to his daughter, he calls her Lily. He apologies and they discuss loving complications. They realize how to move forward on the weapon they’re making.
Barry says his goodbyes to the group, ready to sacrifice himself. They’re already to fight to protect him. Even Cisco, who calls Barry his friend. Felicity realizes the ships are opening, and the metahuman bomb is being lowered.
Cisco and White Canary take the Waverider. Martin brings a weapon he invented. It needs to be placed on all the Dominators before being activated.
The gang, including Supergirl, gets ready to fight on the roof. As they fight a group of Dominators, The Flash speeds around placing the weapons on each one.
Cisco asks if the Waverider has a tractor beam, and Sara uses it to grab the bomb. It slows down, but does not stop. She calls for Firestorm to help.
During the fight, The Green Arrow is thrown off the roof. Supergirl flys out and catches him. Then she and The Flash head out to find all the other Dominators and tag them too.
Firestorm attempts to transmutate the bomb.
Green Arrow gives the signal and Felicity activates the weapon, hurting all the Dominators.
Jax does not think they can change the bomb. Martin begs Jax to try, for his daughter Lily. Together, Firestorm changes the bomb to water.
Around the world, the Dominators retreat to their ships and leave the earth.
The new President honors all the heroes, in a private ceremony. This is followed by a celebration in the hanger. Ray notices that Kara looks like his cousin. Ollie apologizes to Kara. She tells him that hardship makes them stronger. Cisco presents Kara with a new invention. Now she can communicate with them, and make breaches whenever she needs them.
Jax finds Martin and asks about Lily. Martin explains he changed the past and she is the result. He begs Jax not to tell the others, he does not want Lily erased.
Nate confronts Glasses. Kara joins and says that she told the new President about the DEO and she plans on making one on this earth. And that Glasses is being transferred to Antarctica.
Kara says her goodbyes, makes a breach, and goes home. Sara talks to Ollie about like if they had not gotten on the Gambit. Maybe their fantasy world was a gift.
Diggle calls Barry one of the best men he knows and tells him to forgive himself.
Barry and Ollie talk about hanging out when there is not a massive threat. They go out for drinks and discuss how in the Dominator’s fantasy and in Flashpoint, life was normal but not full. They toast a life that is not normal, but always full.