On a train station platform, a man trips another man with his umbrella, then apologizes profusely. The tripped man goes home - and passes out. He wakes up bloody, covered with a paper blanket. The umbrella man calls 911, apologizes again, and injects the victim in the neck. He pats him on the shoulder and leaves as the victim convulses.
A paramedic pulls back the blanket: The victim's heart is gone. Then the man wakes up! He says, "Don't let me die." At the station, umbrella man carries a small cooler.
Olivia fills Broyles in on Walternate's experiments - and his determination to destroy their world. She wants to see the pieces of Walternate's machine. Broyles says that she's still officially on leave. But Olivia wants to work. She promised a friend Over There that she would try to heal both worlds. Broyles asks what his other self was like and learns he was still married.
Heading out to investigate the heartless guy, Walter asks Peter if he told Olivia he slept with Bolivia. Peter says he will, even though he expects it to change things.
At the victim's house, Broyles briefs Olivia and the Bishops. The man regained consciousness and spoke, then died three minutes later. Walter is giddy with excitement. Walter notices the victim had heart surgery before. Peter finds a bunch of prescription bottles, while Walter notes the body still has reflexes and no rigor mortis. Broyles sends the cadaver to Walter's lab.
The doctor who prescribed the meds tells Olivia and Peter that the victim, Mr. Russo, had a heart transplant. But before that, Olivia tells Peter it's weird to know someone else has been living your life. Peter looks uncomfortable. He says that when they returned from the Other Side, Bolivia said she wanted to change her life - and he believed her. He came back to this world for Olivia. And he explained away the small changes in her because their relationship was different - they were seeing each other. He apologizes. Olivia says that Bolivia's loved ones all believed she was her. Why not the other way around?
In a basement lab, the heart thief sews up the chest of a pretty, dead blonde. It won't be long now, he says.
Walter tells Peter he isolated a serum in Russo's blood that radically slows down cell degradation. Peter asks why slow the guy's death after stealing his heart? Walter says it's to soothe the organ thief's conscience, by giving the victim a possible, though highly unlikely, chance of surviving. Peter says that Olivia took the news surprisingly well. Walter wonders if she was replaced with a robot.
In her apartment, Olivia looks at her neck tattoo. One by one, faster and faster, she pulls clothing and hangers off the closet rod. She strips her bed and goes to put the sheets in the laundry. There's already stuff in there - including Peter's MIT T-shirt. She sinks down, weeping.
The next day, Olivia asks Astrid what Peter was like with "her." Astrid says Peter's feelings were about Olivia. They were real - and still are.
The team discovers a series of recent organ thefts, all by the same person. All the organs came from the same donor, 17-year-old Amanda Walsh. Realizing her corneas haven't been stolen, they go to warn the recipient. Too late. In the hospital, the blinded victim says the man actually apologized. Walter was right about the remorse.
Amanda's mom tells Peter and Olivia that the girl was a ballerina - and clinically depressed. Despite group therapy and taking meds, she committed suicide. Walter wants to see Amanda's body, but she was cremated. Peter brings Walter her ashes. Walter opens the urn . . . and tastes them! But it's just wood ash and concrete. Walter thinks the organ thief stole Amanda's body and is putting her back together.
Walter's right again. In the basement lab, Amanda is whole. Sitting lifeless in a vintage wheelchair, she's strapped to cables attached to levers: a human marionette. The teary-eyed organ thief plays classical music on an old-fashioned record player and pulls her strings, making her dance. Creepy.
Things are tense between Peter and Olivia as they search files from Amanda's therapy group. He finds the guy: Roland David Barrett, who quit the group the day Amanda killed herself. Barrett did postdoctoral work on cell decay and regeneration, and his later research helped create synthetic life on the cellular level. Could Barrett actually reanimate Amanda?
In his basement lab, Barrett shocks Amanda. The heart monitor beeps. She gasps, breathes, and rolls her eyes. She's alive! When she looks at him, he's happy. Then he pulls back, sobbing. And then the FBI arrives.
Upstairs, Olivia tackles Barrett. He says when he looked into Amanda's eyes, it wasn't her. He doesn't know what he brought back. Downstairs, the others find Amanda, dead.
Afterward, Walter wants a strawberry milkshake. Peter finds Olivia in Barrett's backyard, upset. She tells him what Barrett said about looking into Amanda's eyes. She cries and says when she was Over There, she held onto him . . . so why didn't he? "She wasn't me. How could you not see that?"
Olivia doesn't want to wear her clothes anymore, doesn't want to live in her apartment. And she doesn't want to be with Peter. "She's taken everything." Olivia leaves. "I'm sorry," says Peter.
Time for that milkshake. An Observer makes a call while watching Peter and Walter: "He is still . . . alive."