In a diner in Noyo County in Washington State, a waitress, Krista, is serving her customers and chats with Peter Bishop. She explains that she gives CDs to the regulars based on their auras. Peter hesitates to say exactly where he is from originally, and admits he doesn't know where he's going. They flirt and Krista promises to stop by his hotel after her shift to drop off a CD. Later, Krista closes up for the night and finishes burning the CD for Peter. As she goes, a man abducts her, takes her to a hidden lab, cuts open her skull, and removes a part of her brain.
The next morning, Peter wakes up in the lobby of his hotel. He realizes he dozed off waiting for Krista, but the clerk notes that she never came by. Peter goes to his room and the phone rings. However, all he hears at the other end are strange distorted voices. Peter takes to the road and passes by the diner. The police have cordoned off the area. When Peter gets out, Sheriff Ann Mathis and Deputy Ferguson come over and asks what he knows about Krista. Mathis goes to confirm his alibi, while Peter scans the crowd of onlookers and sees Newton. He starts to go after him but Mathis stops him. She wants to take him to the station to answer more questions. As they drive, Peter admits that he was staying under an assumed name.
As they proceed, Mathis gets word that the teams have discovered a corpse. They stop at the river where the dogs have turned up Krista's body. Peter listens as the radio reports that a piece of her skull was cut out. When Mathis returns, Peter asks if a part of Krista's brain is missing, and asks Mathis to confirm with the coroner. She reluctantly does so and tells Peter that his suggestion was correct.
At the station, Peter identifies himself as a civilian consultant to the FBI, someone who deals in the strange and inexplicable. He explains that the removal of the temporal lobe occurred in another case, and suggests that Newton and his people are tracking Peter, and called him at the hotel. Peter figures that they removed the piece of brain to examine her memories of him in detail.
As Mathis goes to check Peter's credentials, Peter calls Broyles and asks him to verify his credentials. Broyles agrees, and Peter asks him to keep Walter out of the loop. his superior agrees, but offers to send someone whenever Peter is ready.
At the morgue, Peter explains that the human brain retains everything it experiences. They examine the body and realize that Krista was suffering an adrenaline rush right up to the moment she died. As they work, Mathis drops a pen that she admits was a gift from Ferguson, the only officer who believed in her. Afterward, Peter signs his statement and checks in at a different hotel, and vows to find the people responsible. After he goes, Ferguson wonders if Peter is legitimate, and notes that Mathis is obsessed with UFOs and conspiracies. She insists that she's a good judge of character.
Peter goes to see a gun dealer and buys a shotgun and ammo. Back at his hotel room, Peter receives a call and answers it. It's the same strange electronic voices. He hangs up and it rings again, and it's Mathis. She tells him that Ferguson has disappeared. Peter comes in and Mathis figures that they abducted Ferguson for the same reason they abducted Krista. The sheriff wants Peter to call in the FBI, but he warns that if the FBI comes in, they'll lose Newton and his people. Mathis then tells Peter that according to the phone records, there were no calls to his room. She starts to call the FBI, noting she has no reason to believe Peter, but he stops her and insists that everything he's said is true. Mathis stops, but worries what will happen if she doesn't do everything possible. Peter insists that his way is best.
In Boston, Walter is shopping and flies into a rage when he discovers there's potassium bromate in the food. He finally snaps out of his rage and then collapses, sobbing. Olivia and Astrid come to get him after he's taken to the police station, and he admits the place is a mess. Astrid asks why he didn't ask for help, and Walter explains he needs to learn to care for himself in case Peter doesn't come back. He worries that he'll be sent back to St. Claire, but Olivia promises that she won't let it happen.
Peter and Mathis go to the bridge where Ferguson said he was going to visit. They separate to look around and Peter finds a Bazooka Joe comic on the ground. He hears an electronic warbling sound in the woods and goes to investigate. Newton and another man are there, see him, and fire a dart at him. Peter returns fire but they disappear. Mathis comes running as Peter tries to find Newton, catching brief glimpses of him between the trees. The sheriff finally catches up and he asks if she saw him. Peter notices that there's blood on her sleeve and points his gun at her, believing she's a shapeshifter. He finally confirms who she is based on the pen she had at the morgue, and she says she cut her wrist when she fell while running to investigate the gunshots. Peter apologizes and explains about shapeshifters. Mathis admits that she believes in the unknown, but thinks Peter is imagining things. Peter figures there's something between the two of them, and Mathis admits that she has feelings for Ferguson, and won't admit he's dead until they find a body.
Mathis is called to a quarry where a body has turned up. They discover that it's the body a girl that Peter doesn't recognize. The girl is Gwynn, and they talk to her sister, Heather. Peter questions her about whether Gwynn was anywhere that Peter had been. Mathis stops him and warns that Heather is grieving.
At home, Walter puts on a record and thanks Astrid for helping him. She finds a double-decker car model that Walter brought over from the other side, and asks Astrid to bring all the objects from the other universe to the lab so he can identify their glimmer and use it to find Peter.
As they drive home that night, Mathis insists that Peter stay with her that night so she can keep an eye on him. They find Gwynn's truck and realize that someone posing as a cop got her to pull over. Peter suggests that a shapeshfiter disguised as Ferguson pulled her over. Mathis prepares to call in the FBI but Peter realizes he has a way to find the killers. They go to the morgue and Peter examines the two bodies. He concludes they can measure the adrenaline spikes and use the intervals between the two spikes to learn where they were killed. He then fires a shoot to get her adrenaline pumping, and takes a tissue sample to use as a control.
Olivia meets with Broyles and tells him about Walter's concerns. She insists that Peter will come back and Walter will be able to function normally again. However, Olivia realizes that Broyles has spoken with Peter.
Peter calculates the distances that each victim traveled, and Mathis realizes there's a dairy farm in the area indicated. They go to see the owner, Craig, and Mathis asks a question to confirm he's the real Craig. They then go over a map of the old dairy farm. Mathis goes to call for a search party. While Peter waits, he notices Krista's CDs on Craig's shelves, including the one she was going to give to Peter. Craig attacks him but Peter quickly subdues him and demands to know where Newton can be found. Craig explains he couldn't stop and just wanted to be close to the girls. Mathis demands to know where Ferguson is. They go to Craig's makeshift operating theater and find Ferguson, still alive.
Later, Peter apologizes to Mathis for being wrong, but she thanks him for saving Ferguson and locating the killer. She wishes she could help him, and Peter admits that he doesn't know who he is anymore. Mathis explains that her family was killed when she was in college, and that she still hopes to find the killer one day. Now she's found someone, and she hopes he will, too.
At the lab, Walter works to pinpoint the alternate-world glimmer. However, Astrid notes that he entered the wrong numbers, and realizes that he did it deliberately. Walter wonders if Peter won't forgive him, and what he can do if that happens. Olivia arrives and tells Walter that she's found Peter in Washington State. She invites him along and Walter agrees.
At the hotel, Peter plays Krista's CD and dozes off. He wakes up to find Newton in his room. Newton holds him at gunpoint and calls in Mr. Secretary. The visitor from the other Earth enters: Walter Bishop, who says, "Hello, son."