It's snowing as Barry sits in his apartment with Iris, calculating how far in the future he needs to go to learn Savitar's identity. He settles on 2024. Iris wants to have a serious talk about what might happen after she dies. She makes Barry promise that he will be there for Joe, no matter what. He agrees, but their conversation is interrupted by an alert from STAR Labs.
Killer Frost is attacking Cisco, Julian, and H.R. She wants to kill them to make sure they don't try to bring Caitlin back. They attempt to hide in a cell, but she can still access it. Barry arrives, and manages to save them, but Killer Frost gets away. He decides to go after her later. His priority at the moment is going to 2024. Wally helps him create a portal.
When Barry arrives in the future, he encounters Top and Mirror Master. He speeds away from them and goes to the loft. It's a disaster. Cisco arrives. He had a feeling something was happening. But Barry can't explain because of the rules of time travel. Cisco explains that the team fell apart. Caitlin never returned. Barry pushed everyone else away. He's living at STAR Labs. Cisco brings Barry there, and asks him not to leave without saying goodbye.
Future Barry is a mess. He never recovered from losing Iris, and he hasn't used his powers in years. He tells Barry to go home and spend as much time with Iris as he can before she dies. Disappointed, Barry plans to go back, but Cisco asks him to stay. He wants him to reunite the team. Barry tries to go back to the past, but something is stopping him from accessing the portal.
Cisco reveals Killer Frost destroyed his hands in their battle. He can no longer vibe. He takes him to see Julian, who's watching over Killer Frost in a cell. She knows who Savitar is because she teamed up with him in 2017. Barry goes to the West house, and finds Wally in a wheelchair. He attacked Savitar and ended up paralyzed and catatonic. Barry finds Joe at the cemetery. He's heartbroken over losing his children, including Barry, who turned his back on him.
Barry confronts Future Barry for breaking his promise to Iris. Future Barry tells him that he doesn't understand what it's like to have Iris die in his arms. It will break him. Barry realizes Cisco is the one keeping him there. Cisco admits he wanted the team back together, and he missed his friend. Barry agrees to stay, and rounds up the team. Joe, Julian, H.R., and Cisco all help Barry face off against Mirror Master and Top. But when he's not enough, Future Barry steps in to help, too.
Team Flash agrees to reunite. Future Barry tells Barry about a physicist named Tracey Brandt. She's the one who helped him trap Savitar in the Speed Force. But she didn't discover the technology until four years after Iris died. Future Barry gives it to Barry and hopes he can find her. If not, he tells him again to take advantage of the time he has left with Iris.
Back in 2017, Barry tells his friends he may have a lead. Julian asks what he learned about Caitlin. Barry explains she teamed with Savitar. He says they need to find her. Team Flash is on the case. But Savitar's already found Killer Frost and offered her salvation. He says he has a way to make sure Caitlin Snow never comes back. When she asks why she should trust him, he reveals his true identity to her, and she immediately agrees to help.