Four years ago, at Coeur d'Alene, Idaho, Nora Havelock pulls up to a cabin and goes to the door. Sam greets her and says that she shouldn't have come. Nora says that she had to see after all the years of reading and hunting. Sam takes in the Wiccan to where Dean is guarding a demon-possessed human. There is a corpse nearby and Nora tells the demon that it's going back to Hell, but it promises to track her down and kill her. She runs out and the Winchesters tell it that they plan to torture it for information on Lilith. The demon lets its human host, Jeffrey, speak out. He says that they have to stop the demon and begs them not to hurt him. However, Sam warns that they have to torture the demon to get the information they need, which means they'll have to torture him. Jeffrey tells them to do what they have to just to stop the evil. The demon takes control back and Dean tells him that Jeffrey agreed to the torture and then the brothers start torturing the demon with the demon-killing knife and holy water. The demon finally tells them they want a demon named Merrick in New Orleans. Dean then exorcises the demon out of Jeffrey.
Dean drives Jeffrey to the hospital and tells him that the demon is gone. He drops him off and tells him not to tell anyone about the demon., and then drives off as Jeffrey mumbles a thank-you.
Now, Sam and Dean check into a motel in Coeur d'Alene and get a call from Frank. While Dean talks to their contact, Lucifer appears to Sam but Sam manages to concentrate and drive the hallucination away. Frank admits that he hasn't had any luck finding Dick Roman. Dean and Sam go back to the case, which involves that someone is committing the same types of murder that their demon did four years ago. Two women have been killed but Dean says that they need to worry about the Leviathans, Sam disagrees, saying that they need to take care of their old case.
That night, the brothers pick up a report on the police scanner of a new murder. They pose as FBI agents and run into Detective Sutton, who remembers them from the first time. Sutton figures it's the same killer since they didn't catch him last time. Sam checks the victim's SUV and finds traces of sulfur nearby. They go to see Nora at her shop, and she explains that she knows about the new murders. She has been working on demon traps and banishment rituals, but admits that she was in over her head four years ago and will leave it to them. Dean notes that she helped but Nora admits that she's going to leave town. She asks them about Jeffrey and suggests that the demon might have gone back to the same host.
Jeffrey is at a halfway house meeting with his fellows. He explains that he's getting a dog and assures the man in charge, Alan, that it's about responsibility. He picks up the dog from the animal shelter and nervously walks down the street. He hears something in a nearby alley and reluctantly goes to investigate. Sam and Dean grab him and make sure that he's himself, and then have him take them to his apartment. As Sam tries to reassure Jeffrey, Lucifer appears briefly to Sam but then disappears when he realizes Sam is going to dismiss him. Dean tells Jeffrey that the demon is back and Jeffrey wonders how that is possible. He then tells them the name of the next victim, Marjorie Willis, and explains that he knows it because the demon had made a list four years ago and told him over and over about it. When the brothers wonder why the demon would be a serial killer, Jeffrey tells them that the demon said it was his job.
Alan knocks at the door and Jeffrey tells him that Sam and Dean are friends from when he worked at the post office. The brothers listen in and realize how bad Jeffrey has had it. Dean stays with Jeffrey while Sam goes to the library to find Marjorie. Lucifer points her out at the librarian's desk and tries to get Sam to acknowledge him without success.
Jeffrey tells Dean what happened to him afterward. He lost his job and his health insurance, started drinking, and had a mental breakdown. Jeffrey started to talk about what happened and got put into psych eval and then an institution. Dean admits that he knows friends that it's happened to, and tries to comfort Jeffrey by pointing out that he got out. He apologizes but Jeffrey insists that he owes him for saving his life. He then hesitates and then tells Dean that he might know where demon is. Jeffrey explains that it had a special place where it nested and kept its souvenirs, and insists on going with the brothers when they check it out.
At the library, a bored Lucifer gives Sam visions of the patrons smashing their heads into the tables. Sam manages to focus past them and then spots a man in a black leather jacket following Marjorie into the shelves.
As night falls, Dean and Jeffrey drive to the demon's lair near a train yard. Jeffrey gives the dog some jerky and tells it to stay, and then explains that the demon only let him go so far.
Sam follows the man and discovers that he's making out with Marjorie between the shelves.
Dean and Jeffrey enter an abandoned building and Jeffrey finds the way to the demon's nest. The windows are covered in demonic symbols and Dean tells Jeffrey to stay put while he investigates further. He finds someone chained to a chair and goes to free him, and Jeffrey injects Dean in the neck with a sedative.
As Lucifer continues to mock him, Sam calls Dean but gets no answer. He goes over the coroner report and Lucifer points out that all of the victims had tranquilizers in their system, and a demon wouldn't have needed to drug its victims. Sam finally acknowledges Lucifer by telling him to shut up and then goes back to Jeffrey's apartment. He finds the box for a cell phone scrambler and Lucifer suggests it's the reason why Sam can't reach Dean on his phone. Sam continues searching and finds a secret compartment with a spell on it in Latin. He realizes that it's a demon summoning spell and Lucifer points out that they both know the handwriting.
Sam breaks into Nora's shop and she attacks him. Sam easily subdues her and asks why Jeffrey had a demon summoning spell in her handwriting. Nora insists that Sam can't change anything, and he threatens her unless she explains. She finally tells him that Jeffrey has her son.
Dean wakes up tied to a chair next to the man from earlier, Nora's son. Jeffrey is waiting for him and explains that no one asked the Winchesters to save him, and that he loved being possessed. He prepares the demon summoning ritual while he tells Dean that he loved the demon. Dean realizes that Jeffrey is a serial killer, and Jeffrey explains that the demon made him live up to his potential and taught him how to kill. The list was his, a list that Jeffrey made up as a game because they drew him to them.
Nora explains that Jeffrey came to her and asked for a way to summon the demon back. She told him to get some help, and then Jeffrey abducted her son and told her to provide the ritual in return for the boy's life. He then sent her the boy's ear because the ritual didn't work, and Sam explains that it's locked up in Hell for betraying its master. Jeffrey told her to find out what went wrong and she found a summoning spell that would work for sure. He then told her to send the Winchesters to him. Sam realizes that the spell requires the blood of the exorcist who banished the demon to bring it back. He tells Nora to use her son's ear to cast a location spell.
As Jeffrey bleeds Dean, he says that he realized a lot about Dean as he tortured Jeffrey. He figures that it hurts Dean that people keep getting hurt and he can't do anything about it. Dean denies it but Jeffrey explains that he was depressed and suicidal, but Alan convinced him to focus on his goals and attitude. Jeffrey kills his dog to get the last ingredient: its heart. He pours Dean's blood on it and casts the ritual, and the building shakes. However, the demon appears inside of the boy's body instead.
The demon breaks free of its chains and hugs Jeffrey, thanking him for his help. It dances with Jeffrey and congratulates him for learning his lessons from him. When Jeffrey says that he wants the demon to possess him, it tells him that he's learned his lessons and is ready to strike out on his own. When Jeffrey refuses, the demon slaps him down and tells Dean that he's merely a talent agent, and that he tries to find the hellbound and train them to their full potential. When Dean asks about the boy the demon is possessing, it says that it plans to destroy him because there's no potential.
Sam arrives and attacks the demon, which throws him back. Dean breaks free but the demon steps forward and realizes that they've lured it into a demon's trap that Nora has drawn. When Jeffrey advances goes to the demon to free it, Dean shoots him. Nora begins the exorcism ritual and the demon says that it'll be back. Dean tells it to go to hell and the demon is sucked out, freeing Nora's son. She goes to him and says that she's got him.
Back at the motel, Sam realizes that Jeffrey was acting four years ago. Dean tells him that psychopaths act like they're normal and dozes off. Lucifer tells Sam that he won't be sleeping and suggests that they talk. Sam tries to send him away without success and Lucifer tells him that since he let him in, he can't send him away. The room bursts into flames around Sam as Lucifer laughs in triumph.