Erwin Lukesh enters his apartment building foyer, while Reyes fiddles with the derailleur of a bicycle in the hallway. This is a stakeout being recorded by a hidden camera, as Doggett and Follmer watch from a surveillance van nearby. Lukesh is a wanted killer who removes women’s tongues. This makes Doggett nervous for Reyes’ safety. In order to positively ID Lukesh, the agents wait for him to open the mailbox for Apartment 4-D. Doggett, however, is eager to nab him sooner. Lukesh senses that something is not right, and he moves away from the mailboxes. Reyes takes out her gun and begins to follow him, talking to the agents in the van as she heads into a stairwell. Suddenly, Lukesh appears and slashes a straight razor at her. Doggett and Follmer bolt out of the van when they hear Reyes’ screams. They find her throat cut, and Doggett goes to apprehend Lukesh. Follmer warns him that the killer has Reyes’ gun. Doggett goes outside into a dead-end alley and corners Lukesh, who calmly raises his bloody hands in surrender. Police cars approach from behind, and Doggett turns slightly to let them know his location. When he turns back, Lukesh has disappeared. Doggett walks forward into the dead-end alley. The police cars have vanished, and Lukesh is now behind him. He holds Reyes’ gun pointed at Doggett’s head. When Doggett swerves around, Lukesh fires.
Reyes, unharmed, unpacks boxes as she moves into her new apartment. Doggett pays her a visit. He is also unharmed, and he has brought her a housewarming gift -- polish sausage sandwiches from a nearby stand. Reyes goes into the kitchen to get plates, and her phone rings. It is Skinner, with news that Doggett has been shot in an alley. Reyes is confused when she sees that Doggett is no longer in her apartment.
Follmer and Scully meet Reyes at the hospital. She is convinced they are mistaken about Doggett, since she knows he was just at her apartment. However, she sees for herself that Doggett lies paralyzed in a coma. Reyes tries to make sense of this impossible situation, and Scully recounts her own story of her father’s visitation to her after his death. Reyes is certain that this is not what happened to her. Skinner learns from ballistics that the bullets came from Reyes’ weapon, and he has Scully bring Reyes to the police station. Follmer questions Reyes. As he brings up the evidence against her, she stands by her story. From the observation room, an eyewitness to the crime identifies Reyes as the shooter. The eyewitness is Lukesh.
At the hospital, Scully and Skinner explain to Reyes that the case against her has some weaknesses. When Skinner called earlier, Reyes was at home, putting her fourteen miles from the crime scene. However, while her gun was never fired, the bullets do match her weapon. Doggett awakes from his coma, tapping on the bed rail. Skinner recognizes the tapping as Morse code. Doggett spells out “Lukesh.” Reyes, however, has no idea what the word means. Back at his home, Lukesh tends to his bed-ridden mother. When she’s not looking, he fingers the Sig Sauer pistol he grabbed from Reyes. Mrs. Lukesh asks for her favorite sandwich, and Lukesh pulls the secret ingredient from the refrigerator -- a human tongue. Later that night, Lukesh slips out of the house, but his mother hears him leave. He walks into the alley with a straight razor in his hand. He mysteriously vanishes into thin air.
At Reyes’ apartment, Skinner shows her a file on Erwin Lukesh. Lukesh claims to have seen Reyes exit the alley after Doggett was shot. She believes that Lukesh might somehow be involved. Follmer has Skinner bring Reyes to the hospital, because she is the only one Doggett will speak to. As Doggett maneuvers a joystick attached to a communicator, he asks how Reyes is actually alive when he saw her throat cut. Doggett tells Reyes and Follmer that Lukesh not only tried to kill him, but Lukesh also murdered Reyes. The next day, Reyes asks Doggett if he knows of a food stand near her new apartment. He immediately recognizes it as the best polish sausages in the city. With renewed hope in his answer, she proposes a theory to him. Perhaps Lukesh can move freely between parallel universes, and somehow Doggett followed him through that door. In this other world, Reyes was killed while investigating Lukesh. Yet here, she doesn’t even know the man’s name.
Follmer and Skinner interrogate Lukesh, informing him that Doggett named him as the shooter. They ask to speak to Lukesh’s mother in order to corroborate his alibi. Lukesh refuses the request, which alerts Skinner and Follmer that he is hiding something. As Lukesh walks out, he passes Reyes in the police station hallway. She boldly asks how he moves between worlds to act out his fantasies. He inches close to her face, calmly saying, “God, I enjoyed you. You bled just like a pig.” Lukesh returns home to find that Reyes’ gun is missing from a drawer. His mother confronts him about the gun, as well as his sneaking out of the house. She tells him that the FBI has left messages for her, and that she intends to speak to them. Lukesh begins crying, and pulls out his razor. He approaches his mother’s bed and strikes her.
At the hospital, Doggett types out the message “2 Doggetts cant be in 1 world – U can fix.” He begs Reyes to pull his life support plug, believing in her theory about the parallel universes. If one of him is removed, the other Doggett will enter this world. Their conversation is interrupted by Skinner, calling to tell her that Lukesh killed his mother and then disappeared. Reyes returns to her apartment with a radio wired to Scully, Follmer, and Skinner in a surveillance van outside. They are watching everything in her apartment over video monitors. Suddenly, Lukesh appears from nowhere and grabs Reyes from behind. He pulls the earwig radio from her ear and holds his razor to her throat, fully aware that a van is outside. When the agents lose Reyes on the video, Scully is sure that Lukesh is inside the apartment. Lukesh blames Reyes for making him kill his mother. He is about to slit her throat, when Follmer storms in and shoots him, saving Reyes.
Late that night, Reyes goes to the hospital with her decision made. She turns off Doggett’s respirator, and he takes his last breath. Crying, she closes her eyes. When she opens them again, she is no longer in the hospital. She is in her unpacked apartment, as she was before, and Doggett tells her to forget the plates for the polish sausages. She is stunned and overwhelmed at the sight of him. He wonders what is wrong with her, as she tearfully hugs him. “I’m good,” she happily cries.