Sam and Dean learn about a monster killing in Chicago and head there to investigate. What they find is a young cop whose girlfriend was killed by the same creature, and who is caught between five powerful clans of monsters who jointly control the city.

Sam and Dean investigate a series of werewolf attacks.

Sam and Dean investigate a string of suicides committed by people with little in common other than the identical, grisly method of death – slow, self-administered disembowlment. All of the victims were members of a Catholic church and had recently given confession, leading the brothers to suspect the priest is somehow involved. Meanwhile, when Crowley captures Olivette, the leader of the Grand Coven, Rowena pleads her case to be allowed to practice magic freely again.

After a construction worker is killed by insects burrowing into his brain, Sam and Dean investigate the town's history and find that the new housing development is being built on sacred Indian land. The Indians put a curse on the land after their reservation had been ravished and destroyed. Sam and Dean must find a way to survive and kill the deadly swarm of bees, locusts, spiders and beetles.

After the massacre at the ranch, Dean, Sam, and Castiel double their efforts to find a cure for the Mark of Cain. Desperate, Castiel comes up with an idea that Sam deems the single worst idea he's ever heard. Meanwhile, Rowena continues to plot against Crowley.

A ghost starts killing people through various electronic devices. Sam and Dean discover who was killed and why this ghost is seeking revenge on a group of college students but what they can't figure out is how he’s doing it. With three dead, the brothers must stop the ghost before he claims his next victim.

Despite Dean's directive to forget about looking for a cure for the Mark of Cain, Sam continues to do research. Dean suspects Sam is hiding something but decides to focus on a new murder case where they run into Cole. The three team up and learn a Khan worm is infecting men and turning them into murderers. Unfortunately, the worm makes its way into Cole.

Sam and Dean discover a group of witches on a gone wild trip and attempt to stop them.

It's the final ride for the Winchesters saving people and hunting things.

After Dean hears a surprising message on Bobby's phone, he and Sam head out to investigate.

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

When Claire Novak gets a lead on her mother, Amelia, who has been missing for years, Castiel asks Sam and Dean to help her. However, when they find out what took Amelia, they realize there is a chance Claire may not get her happy ending.

In a change of pace, Sam and Dean decide to star in a violent, profane reality show named Ghostfacers. The show takes them to the haunted Morton Mansion, and they soon realize they're in over their heads.

Sam and Dean investigate a bizarre murder in a college town. Close on the tail of their suspect, they bust into an apartment to find two dead bodies and a laptop cued up to some disturbing video footage.

Sam continues to try to save Dean from the Mark of Cain. Realizing that Dean's antics are causing problems for him in hell, Crowley seeks help from a reluctant Castiel.

Castiel finds Jimmy’s daughter Claire in a group home and she convinces him to break her out. After she runs away from him, Castiel calls Sam and Dean to help find her before she gets in trouble.

Sam and Dean search for a Crocotta that uses the phone and computer as a means to communicate with people. Its goal is to get people to commit suicide and take their soul. Dean gets some news from an unlikely source about a demon holding the contract to his soul.

The Winchester brothers investigate a murder that was apparently caused by a ghost. Sam and Dean discover that the Ghostfacers, Ed and Harry, are already on the case.

Dean and Sam investigate a bizarre murder and realize the killer bears the same tattoo as those from the Styne family. Meanwhile, Castiel acts as referee when Charlie and Rowena are forced to work together on the Book of the Damned. When Crowley discovers that his mother is missing, he turns to an old enemy for help.

Sam and Dean are alarmed when they learn hunters are being killed by suspicious “accidents” all over the country. They decide it is best to find Mary and make sure she’s safe. Meanwhile, Toni is back in the states and she and Mary face off.

Sam and Dean are asked to investigate the murder of a childhood friend, calling them back to a motel from their past and perplexing the brothers with a case they thought was solved a long time ago.

Dean is contacted by his first love Cassie, an African-America girl, who asks him to come to Mississippi to investigate a string of racially motivated murders. Each murder is linked to a mysterious truck that seems to have no driver and leave no tracks. Sam is stunned to see this new side of his brother as Dean struggles to come to grips with the residual feelings he has for Cassie.

A police officer named James, who turned to witchcraft after working a case with Sam and Dean, is plagued by nightmares in which he murders innocent people.

Sam and Dean investigate some recent vampire kills and are surprised to learn Krissy Chambers is involved. They find Krissy and learn her father was killed and she’s been taken in by a man named Victor, who has taken in a group of orphan kids to teach them how to hunt.

Dean is a demon and running amuck with Crowley while Sam tries to figure out what happened to his brother. Meanwhile, Castiel is dealing with his fading grace.