At a police station, Detective Peter Sheridan goes over a suspect with multiple aliases. As he goes in to talk to a prisoner, SWAT agents lead by Sheridan's partner Diana Ballard close in on a hotel room. Sheridan talks to his suspect about his torture and murder of a woman in St. Louis, and warns him the woman who died in St. Louis wasn't the only one. It turns out he's talking to Dean, while Ballard arrests Sam in the hotel room.
Sam wants to know why Ballard is holding them and she notes that Sam disappeared for a while and reviews his background. She notes that Dean apparently faked his own death in St. Louis and they're digging up his background and exhuming his corpse in St. Louis. She notes they caught Dean at the scene of another mother woman's murder in Baltimore, Karen Giles. Sam finally talks about how another dead man, lawyer Tony Giles, was a friend of John's and they came to investigate when they heard about how he died.
Dean and Sam figure out that the killer left no traces at the murder scene and visit his wife Sarah, posing as insurance investigators. She says that Tony had a vision of a woman standing at his bed. Ballard points out they were spotted at the crime scene and supposedly asked them to get something from the office. The brothers break into the office to check out the murder scene and find that he typed the name Dana Shulps repeatedly and Sam spots the name outlined in his breath on the desk. They turn up nothing on the name and Sam (slowly) breaks into Giles' computer. Dean gets bored and goes back to Karen's place to check up on her. Ballard points out that Dean left him to commit the murder and they got a 911 call of Karen saying someone was in the house. It turns out Karen saw the woman at her window and then her printer started printing out the name Dana Shulps. The mysterious woman confronts her while Dean arrives at the house. He comes in and finds Karen dead with her throat cut and the printer with Dana Shulps name on it. Two policemen arrive and find him over Karen's body and they take him into custody.
Ballard meets back up with her partner Sheridan and notes that the two brothers' stories match, and all they have is circumstantial evidence without a confession. It turns out Sheridan was a friend of Tony Giles and the two partners are having a secret romantic relationship. Separately, both Dean and Sam try to work out what "Dana Shulps" might mean, while Dean's public defender Jeff Krause arrives. With his help Dean figures out that it spells out a street name, Ashland, near the station. He tells Krause to get hold of Sam while Ballard's computer starts typing out the words "Dana Shulps."
Krause starts to meet with Sam but Ballard sends him back to Dean, who has decided to confess. Krause advises him not to but Dean makes a statement and "confesses" that a vengeful spirit is responsible for the deaths and he's not involved. He talks about what they know about Ashland but Sheridan is disgusted and accuses him of the murders and claims a shapeshifter murdered the girl in St. Louis. Sheridan has Dean taken away and then they go back to discover Sam has escaped.
Ballard goes to the rest room where all the faucets turn on by themselves and the words "Dana Shulps" form in the mist on the mirror. The ghost appears, its throat cut, and advances on Ballard before disappearing.
Ballard wants answers from Dean about the ghost and he talks about how they're created by a violent death. He notices a bruise on her wrist, the same that he saw on Karen's corpse. Dean sends her to the place where Sam is holding out and Ballard tells him what she saw. Sam shows her some photos he came up with and one of is the ghost woman, Claire Becker, who disappeared 8-9 months ago. She was arrested twice before her death for selling heroin and Sheridan and Ballard worked in vice. Ballard doesn't remember her and Sam says they should go to check out her place and to salt her bones and put her spirit to rest.
At the apartment, Sam and Ballard check out the place but Becker's ghost appears and advances on Ballard reaching for a window. Sam arrives and Becker disappears, and they check out the window which has "Ashland Sup" written on it--the full anagram of "Dana Shulpa." Sam scans the place and finds her corpse, with bruised wrists and a cut throat. Ballard recognizes a necklace on the corpse as a custom-made piece of jewelry that she also has: Pete gave it to her.
Sam realizes that Becker was trying to warn the victims, and Pete was the one who killed the Giles couple. Ballard talks about how some heroin went missing a year ago but they never figured out who did it, but they need a fence like Becker.
Sheridan is extraditing Dean back to St. Louis himself while Ballard and Sam figure out what's up and go to intercept him. Sheridan pulls off on a deserted road and hauls Dean out of the van, then prepares to kill him why "trying to escape." Ballard and Sam arrive and Ballard tells Sheridan it's over. Sheridan confesses that he killed Becker when she wanted more money, Tony was laundering the money, and Karen knew about it from her husband. Sheridan appeals to Ballard's love for him and she appears to consider, then shoots him in the leg. He still manages to attack her and grab the gun, but Becker appears and distracts him long enough for Ballard to shoot and kill Sheridan.
Come dawn, Sam assures Ballard that Becker is now at rest and she says she can get the Baltimore charges dismissed. She can't do anything about the St. Louis charges but agrees to let them conveniently escape and they go to get the car, why wondering why Ballard looks so familiar…