In St. Louis, a man, James Frampton, is paying off a prostitute, unaware that someone is watching them from down the street. As the prostitute goes on her way down the alleyway, she hears something moving but doesn't see anyone. When she turns around, Kevin shows her his badge and puts the handcuffs on. He then grabs her neck and rips open her throat...
...and James wakes up from his nightmare. His dog comes over and jumps on the bed with him and Kevin lies back down, sweating.
The next morning, James goes to the kitchen and looks in the garbage. Inside is his bloody shirt.
The Winchesters check into a motel and decide to call James the next morning. Sam figures that they owe him when he saved their lives, but Dean isn't so sure. Dean goes on a beer run and asks if Sam needs anything. Sam says that he's fine and his brother points out that he has a lot to do to complete the remaining two trials of God. Dean still wants to take on the trials but Sam tells him to stop worrying.
Once Dean leaves, Sam hears a noise at the door. He checks it out and finds a dog sitting there. It runs in past Sam and sits on the bed, and he confirms that it doesn't have tags. Dean pulls up and Sam hastily goes out and tells him that the dog just showed up at the door. However, when they look inside, they find an attractive woman sitting on the bed, wearing the dog's collar. Sam draws his knife and asks who she is, and the woman says that she's a familiar.
The familiar explains that her name is Portia and she belongs to James. Dean is surprised to learn that James is a witch, and she explains that after the case they worked together, James studied witchcraft. Portia tells them that James is now a homicide detective, but he's been suffering from headaches and nightmares. She suggests that they find a way to help and Dean tells her that they're not fans of witches. Portia angrily points out that James has only used his skills for good and tells Dean to drop the bigotry. Dean and Sam both admit that her reaction was hot.
James is drinking at a local witch's club when his friend Spencer Wallis comes in and says that he isn't looking well. James describes his dreams and Spencer tells him that he has to see someone, However, neither one of them know who could help him. Spencer points out that witches don't fit and asks James how he can reconcile what he is with what he does. James tells his friend that Portia is gone and worries that he's pushing her away.
Portia explains that James thinks that he's actually killing people, and then he blocked her from reading his mind. James doesn't trust other witches and can't go to the police, and Portia admits that she went behind James' back to contact them and ask their help.
A blind man is walking through a park and James watches him from the shadows. James finally steps out and rips out his throat... and wakes up from his nightmare.
Sam and Dean go to James' place and he snaps at Portia, insisting that it's none of her business. She turns into her dog form and walks out, and James comes to talk with the brothers. Dean still isn't happy that their friend is using witchcraft but Sam gets James to focus on the murders. James has confirmed that the people he dreamed about actually died, and he shows them his bloody shirt. Dean suggests that another witch is hexing him but James says that he's never heard of it. The brothers agree to help and Dean takes out a pile of iron chains.
Back at the motel, Sam checks the crime reports and confirms that they all match up with James' description. He was promoted to homicide detective practically overnight and has a 100% success rate. Dean has gathered the ingredients for a witch-killing spell that Bobby taught them, but is worried that they might fail. Sam wonders if he's worried about the spell or about him, and Dean admits that it might go too far for him to intervene. His brother takes offense, saying that maybe he can pull it off, and wonders why Dean doesn't trust him. Sam has realized that Dean only trusts him, but Dean refuses to discuss it. He warns Sam that once they have the spell ready, they'll have to use it on the enemy witch... or James if there is no other witch. Sam points out that they've given other monsters a pass, but Dean points out that James chose to be a witch.
Sam goes to the station and meets with the coroner, Josh. Josh introduces Sam to the lead detective, Ed Stoltz, and Sam shows him a piece of fabric that they found with the blood on it. He gives Ed James' shirt and suggests that they run a blood test. While Josh takes it, Ed says that they have a witness who confirmed that a man with a suit killed one of the victims. However, he refuses to discuss it any further with Sam.
Portia takes Dean to the witch's club, saying that if there's anything to find out it will be there. When Dean wonders how they met, Portia explains that she was the one who found James. When Dean refers to her as a pet, Portia takes offense and says that their souls are bonded together and they would die for each other. Philippe LeChat calls Portia over and she claims that Dean is a Wiccan. She asks about Spencer and Philippe says that he's around. He then asks about James and Portia explains that the witch community thinks that James is nuts for working as a cop. Philippe tells Portia that some things aren't done, but before he can explain, Spencer comes in. Dean asks him if there's a spell where one witch can control another, and Spencer says that he doesn't think it's possible. He then tells Philippe that it's time to go and Philippe transforms into a cat and leave with his master.
Sam calls Dean and tells him that he got back the blood work on the shirt. It matches the blood of victim number three and the brothers figure that James is the killer. They take him home and Portia chains James to his bed. He assures her that it's okay and that one way or another, he'll do the right thing. Portia says that she loves him and they kiss. However, Portia suddenly gets a flash of James' mind, and sees him killing the four victims.
Dean and Sam enter the house and prepare the spell. When they go to the bedroom, they find James chained to the bed. Before they can cast the spell, Portia comes out of the closet and tells them that it's not James. She explains that they were sexually intimate even though familiars and witches aren't supposed to. All Portia saw was the kills: no motive, anticipation, or preparation. She thinks that proves that James is under someone else's controls and asks them to check out her theory since James is chained up.
Sam goes back to the station and meets with Josh and Ed. As Josh leaves, Ed points out that the case is cold and wonders why the FBI is interested in a small-time series of murders. Sam asks how he's doing without James, claiming they worked a case together, and Ed says that they're doing fine and that James' quick promotion didn't bother anyone. Once he leaves, Sam checks the office he came out, C-110, of and discovers that it's locked.
Dean and Portia drive to a warehouse to meet a warlock, Drexyl, who works for James as a snitch into the witch community. While they wait, Dean asks Portia which one she considers herself, a dog or a woman. She figures Dean is interested because of what she said about sex and Dean finally admits that's the reason. Drexyl drives up and tells them that there's no word on the street of a witch hexing another one. He says that there is a lot of chatter that James has turned killer, and that the witch community will give James the choice to leave town or kill himself. Portia says that she won't let it happen and Drexyl warns her that the other witches will do it for him.
Sam meets back up with Dean, who has been checking Bobby's records. He's found a spell that lets a witch project false memories into another witch's mind. Sam tells Dean that Ed said the case is cold but he saw Josh with a case file with James' name on it. As they go to check on James, Sam admits that he's impressed that Dean hasn't made any bestiality jokes. The brothers talk with James and tell him about their suspicions, and James offers to astrally project himself there. The brothers agree to remove the iron chains, but only if James takes them with him.
Once James is freed, he touches the brothers and then casts the spell. He projects himself astrally to room C-110 and they see Ed and Josh compiling information on the victims… and tying it to James. They also have a witness statement from Philippe LeChat, placing James at the scene of one murder.
James breaks the spell and explains that Ed always wanted a breakthrough case to make his career. On his first case, they dropped Ed as lead detective. Portia points out that Ed would need proof and Dean tells her that Philippe testified against James. James loses his temper and knocks the brothers out with a spell. Portia says that they should do it together, but James says that her time with him is done. He screams at her, telling her to go, and Portia reluctantly leaves.
At the bar, Philippe is discussing braces when James grabs him and demands to know why he's lying about him. The familiar insists that Spencer gave him a direct command to lie and James realizes that he's telling the truth. Philippe's neck suddenly snaps and Spencer comes in, having finished off his familiar with a spell. James figures that Ed blackmailed Spencer into doing it, but Spencer explains that he was jealous of James because Portia chose James over him. When they had sex in defiance of witch/familiar tradition, that was the last straw for Spencer.
Dean and Sam come in and Spencer immediately casts them back. James attacks his former friend but Spencer easily resists the spell and lifts James into the air. When Dean tries to cast the spell, Spencer freezes both of them and digs out the memories of their worst traumas. Portia charges out in her dog form and attacks Spencer, disrupting his concentration. As he knocks Portia back, the Winchesters throw the spell and kill Spencer.
Later, James and Portia prepare to leave town. James admits that the witch community doesn't want them and Ed has a solid case against him. Portia admits that she'll miss Sam, and maybe Dean. She gets into the car and turns into her dog form, and James drives off. The brothers hit the road and Dean admits that he was wrong about what he said earlier. When he saw the memories and the pain, he realized he made it through with Sam because he trusts him. Dean figures that if Sam says that he's good then he's with him 100%. Sam says that he's good… and conceals the fact that he's coughing up blood.