While on a hunt, Sam runs into someone from his past and a confrontation ensues. Meanwhile, Dean reluctantly teams up with a quirky, laid-back hunter named Garth, when he finds himself in a situation that he just cannot explain.

Sam and Dean get a call from Annie Hawkins, an old hunter friend, asking for help on a case. When they arrive in town, they find out Annie has disappeared. They trace her last whereabouts to an old abandoned house that is haunted by a powerful ghost.

Sam and Dean investigate a murder and find Garth is already on the case. Dean is not happy to learn that Garth has assumed Bobby’s duties, but Garth points out that both Sam and Dean have been missing for the last year and someone needed to do it. They guys discover an "avenging ghost" is responsible for the murders and they need to find the source before the killings starts again.

To track down a killer, Dean uses a spell to talk to a German Sheppard that was at both murders. However, he soon discovers that everything is going to the dogs when the spell starts making him act like a canine as well.

Jody Mills is matched with an overeager partner during a mandatory sheriff's retreat; when a gruesome corpse is discovered, Jody calls Sam and Dean to help investigate.

Sheriff Donna calls Sam and Dean for help after a horrific murder with supernatural elements happens in her town. Sam continues to have visions and asks God for help, which frustrates Dean.