Wally's training is going well. He hits the speed he needs to save Iris. But then he sees Savitar. He keeps it to himself for the moment.
Julian returns from London. Things are awkward between him and Caitlin as they try to figure out what their relationship is. They press pause for the moment to gather with everyone else. No one knows why Barry asked everyone to meet at STAR labs. He arrives with Iris and they tell everyone they're engaged. Everyone is thrilled, but Joe questions why Barry didn't ask his permission. He tells him that he wanted to be spontaneous.
Wally admits that he's seeing Savitar. Barry is furious with him for keeping it to himself. He orders Wally to leave because Savitar might be spying through him. They need to know more about Savitar so Barry asks Julian to go into his mind. Julian refuses. Caitlin thinks it may be because of her. She convinces him that she knows the difference. He kisses her.
Once Julian dons the headgear, Savitar speaks through him. He tells H.R. he survives his future attack. He doesn't tell them where he is, but drops hints about their fate. He explains that he and Barry cannot live at the same time. He's still trapped in the place Barry put him in the future. Barry finds Savitar worshippers with the box he threw into the speed force, but the stone is missing. Julian worries that he'll be the one to betray them, but Caitlin reveals she kept a piece of the stone. She believed it would get rid of her powers. Julian is angry with her for using him.
Wally and H.R. continue training. Wally's not going fast enough. They decide the best course would be for Wally to see Iris' death for himself so he knows what to do. A reluctant Cisco vibes them into the future. Wally is horrified to witness his sister dying. He also notices there's no ring on her finger. He accuses Barry of wanting to marry her for the wrong reasons. Iris is upset. Joe tries to talk to her, but she's not ready to forgive Barry. She loves him and wants to be his wife, but she doesn't want fear to be the motivator. She takes off the ring.
After Julian channels Savitar one more time, they realize he's in the speed force. He has the stone, but the missing piece is keeping him from being whole. He messes with Wally's head again, and sends him visions of his mother. He wants to stop him on his own. Jesse tries to get him to tell Barry, but he refuses. Savitar taunts Wally until Wally unknowingly gives him what he wants. Jesse warns Barry. He rushes to the scene, but Wally's already thrown the stone into the speed force. Savitar sucks him in and he's freed. Savitar and Barry fight. He stabs Barry.
Back at the lab, Caitlin and the others work to save Barry. When he wakes up, Barry's reeling from Savitar saying Wally's another victim Barry failed to save. Cisco remembers the original prophecy of one of them having to suffer a fate worse than death. Jesse runs off in tears, and H.R. comforts her. Joe and Iris don't blame Barry, but they're devastated. Barry and Caitlin each blame themselves. Barry tells her that his fear is what started all of this.