A man, Matthew Hammond, runs from a pursuing car and ducks down an alleyway. The car somehow gets ahead of him and continues the pursuit, and Hammond ducks into a building. He runs up to his apartment and locks the door behind him, gasping for breath. He realizes that the temperature has dropped and turns to discover that the car is in his apartment. It guns its engine and speeds forward, crushing him against the wall.
Dean and Sam arrive in Dearborn and Sam briefly clutches at the cut on his hand. Dean admits that it feels odd to be working a normal case, and Sam thanks him for letting Amy go. They go into the apartment, identifying themselves as FBI agents, and the detective in charge explains that Hammond was apparently crushed to death by a car. Sam confirms that there are EM readings and finds some kind of red dirt on the carpet. Dean figures that it's a ghost and finds an AA chip, while Sam finds receipts for $50 a month that Hammond spent at a place called Jane's.
Sam talks to the AA councilor and says that Hammond had some kind of problem the night before he died. Meanwhile, Dean confirms that Jane's is a flower shop and talks to the clerk. She says that Hammond prepaid for her to continue delivering flowers to a woman called Elizabeth Duren. The brothers go to the address and realize that it's a cemetery and find Elizabeth's grave. She died at the age of 10 and they head back to the hotel to do some checking. It turns out that Hammond had accidentally run her over 10 years ago. Dean, drinking heavily, wonders if Hammond was drunk when he ran Elizabeth over. Sam and Dean return to the cemetery and salt and burn Elizabeth's bones.
A dog chases Christopher Fisher down the streets. He runs into a diner and locks the door, and then runs to the bathroom. No one sees the dog, while Fisher calls 911 and asks for help. However, he sees the dog behind him and it attacks and kills him.
The brothers return to the hotel next day and read a story about Fisher being attacked by a wild animal in the restroom of the diner, and no one saw anything. Five years ago, Fisher was arrested for running illegal dog fights. Sam checks and learns that Fisher worked at a volunteer animal service even after he served his sentence and raised a lot of money to make a difference. Sam wants to go check the body and Dean hesitates, but then insists that he's fine.
The brothers check with the coroner and find the same red dirt on the body. They track it to an abandoned apple farm, but as they drive toward it, a man steps out in front of them. Dean stops the Impala just in time and the man, Warren, tries to catch his breath. They take him to the hotel and Warren says that they won't believe what he has to say. He finally admits that he was put on trial and sentenced to death for robbing a liquor store and killing the wife and owner in 1981. Warren just got out of prison after a 30-year term, but he woke up in a courtroom in a barn at the apple farm. They confirm that Warren was at the same bar that Hammond visited just before he died. Warren is surprised that they believe him and starts describing the symbols in the courtroom. Dean takes Sam out and says that he doesn't see why they have to investigate because the victims are getting what they deserve. Sam insists on going to find the bar and Dean says that he's going to check out the bar. When Sam wonders if he's going there to drink or investigate, Dean says that he hasn't decided.
Sam returns to see Warren, who refuses to go with him. He claims that the people he killed are out there waiting for him. Sam puts him inside of a circle of salt and leaves him with the TV remote, and then sends the symbols to Bobby to look up.
At the bar, Dean orders a double and flirts with a waitress, Mia. She offers to listen to Dean's story and he talks about how he's going behind someone's back. Mia says that it doesn't make any sense to feel guilty and shares a drink with him, and suggests they leave together when she gets off. A man sitting next to Dean at the bar listens with interest.
Sam drives to the apple farm and finds the barn from Warren's description. Bobby calls to tell him that the symbols identify the god Osiris, a judge, jury, and executioner who weighs the guilt of his victims and executes them if they have any guilt. He surfaces from time to time, executes several people, and disappears. When Sam says they need to track him down, Bobby says that they need to get away because Osiris homes in on guilt, and the two brothers have plenty to feel guilty about.
Dean waits outside the bar for Mia, nerving himself for their date. As he receives a call from Sam, a figure grabs him from the shadows and yanks him back, leaving the cell phone to fall on the ground.
Sam tries to call Dean and Mia finally picks up the phone where she finds it and answers. He tells her to wait there while he comes to the bar.
At the hotel, Warren is watching the TV when it goes out and the lights flicker. He inadvertently breaks the salt circle and then runs out into the hallway. His victims are waiting for him on the stairs and he turns and goes back, only to find them waiting for him. The owner draws a gun and shoots Warren dead.
Sam goes to the bar and meets with Mia, and confirms that there is red soil on the ground. He goes back to the barn at the apple farm, and discovers that it is now filled with Egyptian statuary. Dean is chained to a chair and Osiris is dressed in full regalia and seated on a throne. He points out that he listened to Dean talking about his guilt at the bar, and then calls out to Sam, who he knows is in the shadows. Osiris tells Sam to leave before he decides him, but Sam insists that his brother should have a lawyer. Intrigued, Osiris agrees and calls three witnesses, ignoring Sam's objections.
Osiris calls Jo Harvelle as his first witness. She explains that they worked together, and Osiris notes that she admired Dean as a hunter and a mentor. Jo admits that she trusted him and Osiris asks if it was hard working with Dean considering her feelings with him. He points out that Dean got her started on her first case, and asks if she would have chosen the exact same road without him and still ended up dying in a hardware store. When Dean tries to object, Osiris silences him and invites Sam to cross-examine. Sam establishes that Jo idolized her father, a hunter, and that she became a hunter herself to be like her dad. When she tries to talk to Dean, Osiris sends her away and gives the brothers a moment to strategize before he calls his next witness.
Dean says he has no idea who Osiris plans to call next, and Osiris calls Sam. Osiris points out that Sam had a life and a fiancé until Dean showed up and dragged him back into the hunting life. Sam says that it wasn't Dean's fault, but Osiris isn't convinced. He asks Sam if Dean dragged him along so that he wouldn't die alone. Sam says that he's positive it would have happened regardless of Dean, and Osiris says that he believes him. However, he explains that he merely weighs the guilt and Dean's feelings will determine what happens to him. Osiris says that the guilty want to be judged and punished.
Sam calls Dean to the stand and Osiris agrees. He tries to establish for Dean's benefit that he has nothing to feel guilty about concerning the deaths of Jo and Jess. Osiris is amused by Sam's attempts, and Sam pushes the issue, pointing out that Dean has nothing to feel guilty about. The Egyptian god asks Dean if he still wants him to call his third witness. Realizing that he feels guilty about Amy, Dean refuses and Osiris declares him guilty and tells him to get his affairs in order.
Dean and Sam return to the hotel and find the police taking away Warren's body. Sam says that they can figure something out but Dean isn't convinced. Bobby finally comes up with a way to put Osiris down for a couple of centuries, and tells them to stab the god with a ram's horn. Sam does a Google search and confirms that Jewish people use them. He prepares to go to a synagogue to find one, but Dean is worried that Osiris will send Jo after him. Sam reminds his brother that Dean wasn't the one that killed Jo and tells him to do what he has to, to protect himself from ghosts. Once Dean encloses himself in a salt circle, he tells Jo she can come out now and she emerges from the shadows.
Sam breaks into a synagogue and finds a ram's horn. The rabbi comes in and asks why he's there.
At the bar, Osiris is drinking and watching Mia as she talks to another guilty customer.
Jo says that she would never do it on her own and says that Dean deserves better. He insists that she deserves better.
Sam convinces the rabbi and drives back to the hotel.
Jos says that her life was good, but Dean says that she and Sam were kids and he dragged them along just as Osiris said. She says that Dean all kinds of guilt that he doesn't have to. He wonders what happens when he gets rid of the guilt, and Jo tells him that it's time. She turns on the gas stove, the same way that Jo used gas to blow herself up.
Sam goes to the bar to find Osiris while the guilty woman comes out.
The temperature in the hotel room drops and the windows shatters. A wind blows in, breaking the salt circle. Jo apologizes, saying that Osiris is making her do it, and Dean says that it's okay.
The guilty woman gets into her car and Osiris grabs her.
Jo takes a lighter out of Dean's jacket and prepares to light it.
Sam stabs Osiris with the ram's horn. He mummifies in a matter of seconds and collapses to the ground.
Jo drops the lighter, strokes Dean's cheek, and disappears.
The next day, Sam and Dean share a beer and Dean explains that Jo's ghost was the Jo they knew, just a little happier. He then asks Sam why he volunteered to defend him, and admits that he was pretty convincing. Sam asks his brother who the final witness would have been, but Dean lies and says he has no idea. He then asks Sam why he wasn't on trial, and Sam says that he simply doesn't feel guilty because he paid his dues in Hell. He admits that it doesn't make up for everything, but he believes that he can finally move on with his life. Sam says that he feels good and the brothers drive off.