It's 1985 in Reiden Lake, New York, and young Peter Bishop wants to go home. Marching onto the semi-frozen lake with a concrete block tied to a rope around his waist, he smashes the ice. Elizabeth Bishop begs him to stop, but he plunges into the water. She dives in and rescues him as he screams, "Get off of me, you're not my mother! I wanna go home!"
During one of Walter's crossing-over experiments at the day care center in Jacksonville, Florida, little Nick tells young Olivia that he's worried about leaving his teddy bear if they go somewhere. She says, just put him on your feet and he'll come with us. Telling Olivia to concentrate, Walter puts the bear on Nick's feet. His assistant, Ashley, announces his wife is unexpectedly in Jacksonville.
At home, Walter tells Peter the Dodgers do play for Los Angeles, but Peter insists that they play in Brooklyn. He's seen them. Other things are wrong too, but Walter says that Peter's confused because he was very sick for a very long time. Peter shouts that they're not his parents, and he wants to go home!
Later, Elizabeth frets that Peter's going crazy, but Walter insists they can't tell him the truth, even though sending him home isn't proving so easy. It's already been six months. He can't make a device like the one he used to bring Peter over, because the universe can't withstand any more damage. Neither can Peter, she says. Walter just needs more time. The children should be able to cross over and take Peter. He can ride on their feet. At home, Olivia's stepfather yells at her. She runs from him in fear . . . and is suddenly in a field, with a zeppelin overhead. She turns - and is back with her abusive stepdad.
The next day, Peter tells Elizabeth that Walter stole him from the other world at the bottom of the lake. While running errands, they drive past a field of white tulips. Elizabeth explains that they don't usually grow around here, but a professor who missed tulips invented one that could live in this climate. He used his brain and imagination to turn the world into what he wanted it to be. Later, she takes Peter to a toy store, where he picks out a model DC-3 airplane, and she even gets him to smile.
At the center, Walter gently asks Olivia about her black eye. She insists that she fell. He sees her drawing of a zeppelin. Realization dawning, he asks if she made it last night, after she fell? He tells Ashley that he suspects Olivia's crossover was triggered by an extreme emotional response. When Elizabeth and Peter pay a surprise visit, Peter and Olivia see each other through the office's observation window.
Walter conducts experiments on Olivia, aka Subject 13, videotaping them for William Bell. Deciding that fear might be the trigger, but perhaps not fear alone, he engineers a situation in which Olivia suddenly finds Nick covered in blood. She screams - and creates a huge fireball!
Walter cleans the fake blood off Nick, who doesn't think she liked their joke. And now Olivia's missing. Elizabeth and Peter arrive, and he finds Olivia's notebook with drawings of her evil stepdad and the white tulips.
Elizabeth is outraged that Walter suspects Olivia's stepfather is abusive yet wants to send her home, where the unique combination of love and terror apparently stimulates a cortical reaction. He argues that they have to do this sooner rather than later, because the Other Side will eventually come after Peter. He wouldn't sacrifice Olivia for Peter, but for thousands, maybe millions, of others? It would have to be considered. But now Peter is missing too.
On the Other Side, Walternate drinks excessively and obsesses about Peter's kidnapping six months earlier. His marriage is falling apart. At Bishop Dynamic, he swigs from a flask, looks into a room identical to the one Olivia burned . . . and we flip to that room on This Side. Ashley shows Walter the drawing of Olivia's stepdad.
Meanwhile, Peter finds Olivia in the tulip field and tells her what Elizabeth said, about using your imagination to try and change things. She should tell Walter about her stepdad. They hold hands, and it starts snowing. He asks, did you imagine that?
Back at the center, a terrified Olivia dashes into Walter's office. He's sitting at his desk. Crying, she says her stepdad hits her. That's when she crossed over. She hands him her notebook. She saw the blimps, just like he said, in the sky there. Please make him stop hitting her. Then a voice behind her says, "Olive?" It's Walter. He's not at his desk, and he's wearing different clothes.
Shortly later, Walter threatens Olivia's stepdad with big trouble if he harms or frightens her. He tells Olivia that they'll try to figure out a new way tomorrow.
Peter apologizes to Elizabeth for running off. "I'm never going back," he says, "am I?" She says that sometimes we don't get the world we want, but our hearts and imaginations can make the best of it. She promises to be the best mother to him. He calmly says, but you're not her, are you? She pauses, then recites the you-were-very-sick line. Of course she's his mother. Peter nods, then hugs her and calls her Mom.
After he leaves, Elizabeth weeps and drinks alone.
Walternate calls his wife. He knows where their son is. He's holding a drawing of Peter and Olivia. "He was taken to another universe."