There are 24 hours left before Iris is supposed to die. The team is trying to find a plan. Iris asks Barry to run out and get her caviar. As soon as he leaves, she picks up his phone to record a message.
Cisco calls Barry with good news. He's tracked an energy source to ARGUS. Barry and Cisco go to Lyla and explain the situation. The energy is technology from the Dominators. But Lyla will not let Barry have it. She doesn't trust him after he changed time too many times. Barry decides to steal it. He travels to Siberia 1892 to borrow Captain Cold from the Legends.
Savitar-Barry is making repairs to his suit. Killer Frost questions whether he can really kill Iris since he has all of Barry's memories. He tells her that his life was created to be disposable. He gets a memory flash and sees what Barry is planning with Captain Cold. Killer Frost asks if she should stop it, but he has other plans for her.
Barry and Captain Cold break into ARGUS. They find the alien technology being guarded by King Shark. Barry wants to kill him, but Captain Cold tells him that the cold will put him to sleep. That works. Barry gets the tech, but Captain Cold gets trapped with King Shark. He tells him to leave, but Barry calls Cisco for help. He rescues him, but Lyla catches them. She watched them on the monitors and agrees to give Barry the tech.
He returns Captain Cold to Siberia. Before he leaves, Cold tells him that he needs to stop trying to out villain Savitar. His goodness is his strength.
Wally takes Joe and Iris to Earth-2 to stay with Harry. Joe and Iris confess secrets of their past. Joe sings her a song. Back on Earth-1, H.R. reveals their location to Barry, but it's Savitar-Barry in disguise. He heads to Earth-2, fights with Wally, and takes Iris before Barry can get there.
Cisco tries to make H.R. feel better as the team plans to battle Savitar. Cisco has a vibe of fighting Killer Frost and confesses to Barry that he's known all along this is happening. Barry urges him to go and try and save Caitlin. Cisco seeks her out, but she doesn't want to fight. She wants to kill him.
Tracy's trap is set. Savitar brings Iris to the spot where Barry watched her die. Joe and Harry are waiting nearby. Barry fires the trap at Savitar, but he's prepared for it. That's what he needed the philosopher's stone for--to counteract the trap. As he prepares to kill Iris, her message to Barry is revealed. She recited wedding vows. Barry rushes to stop Savitar, but it's too late. He stabs Iris.