Barry and Savitar Barry face off. The future version of Barry is a time remnant. He needs Iris to die so the present Barry will be in enough pain to eventually create him. Present Barry is confused by the timeline. He thinks he can kill Savitar Barry and end things now. But Savitar Barry explains that cause and effect is tricky. Barry's messed with time so much that the rules no longer apply.
Barry returns to the lab and fills the rest of the team in on Savitar's identity. Cisco and Julian try to explain the science behind everything. Wally wants to know why Savitar Barry is intent on killing Iris. Barry doesn't answer the question. When he and Iris are alone, he admits he recognizes the pain in Savitar. Iris assures him that he's not alone.
Cisco experiments on Barry's brain. He plans to take away his short term memory so they can cut Savitar Barry out of the loop. But when Barry wakes up after the procedure, he doesn't remember anything, including his own name. Julian realizes they forgot to allow for Barry's powers affecting their calculations. Joe and Iris take Barry to the station to meet with Cecile. She needs him to testify against an arsonist. Julian tries to help by feeding him the answers, but the link breaks, and the case is dismissed.
After Savitar also loses his memories, Killer Frost wants to help fix Barry. Cisco tries to reach Caitlin. Meanwhile, Iris tells Barry about their lives together. He's much happier than Barry normally is. Joe realizes Iris wants to let him stay that way. But without Barry's memories, Wally never gets his, and the city is unsafe.
Cisco, Julian, and Caitlin trigger Barry's memories. But he still has amnesia. Iris talks him through his mother's death. Once everything comes back to him, Barry, and a newly powered Wally, fight a fire and save the day. Killer Frost prepares to go back to Savitar, but Barry, Cisco, and Julian try to stop her. Julian professes his love. Killer Frost doesn't care, but when she steps into the elevator, Caitlin breaks through for a moment.
Barry tells Iris that he needs the pain. But he needs the love, too. H.R. and Tracy come up with a potential solution: a huge dose of energy. But there's no source for that kind of energy. The final shot shows King Shark, indicating he is the energy source they need.