Sam and Dean are surprised to discover that Castiel has escaped from Purgatory, but doesn't remember how. Meanwhile, Kevin and his mother turn to a witch for help against Crowley but she betrays them to the King of Hell.
Dean goes to help Benny, who has run afoul of vampires guarding his Maker. Left alone, Sam thinks about his year of retirement, but is soon called back in when Dean calls him for help.
The Winchesters track down a killer and the investigation leads them to found footage of three college students investigating mysterious animal attacks.
After a series of brutal murders where the victims had their hearts torn out, the Winchesters track down and locate the killer. However, they soon realize that he's not the only killer and the others are still at large.
Crowley takes Kevin's mother hostage in an attempt to recover Kevin as he searches for the tablet. The Winchesters help Kevin rescue her, only to discover that she insists on joining them on their quest.
One year after their battle with the Leviathans, Sam finally finds his brother Dean, who reveals what happened to him and Castiel in Purgatory. They soon reunite with the prophet Kevin and learn about another Word of God... and an unbelievable opportunity.
The Winchesters and their allies, including Bobby, Castiel, Meg, and the Prophet Kevin, must try and stop Dick Roman and his Leviathans in a final showdown.
Dean and Sam must search for three key items in order to defeat Dick Roman and the Leviathans. Their quest takes them Crowley and the Alpha vampire, but the Leviathans will stop at nothing to kill the Winchesters and put their plan for global domination into effect.
Meg summons Sam and Dean when Castiel wakes up. However, the brothers have other problems on their hands when they get word of a teenager who has been struck by lightning and become a prophet, and may hold the key to defeating the Leviathans.
The brothers get word that Dick Roman has obtained Frank's hard drive and is using an unsuspecting hacker to decrypt it. While the Winchesters try to find her, Bobby tries to help them but finds himself giving in to his rage against the Leviathan CEO.
An old hunter acquaintance calls Sam and Dean in to investigate a haunted house, but when she disappears before they arrive, they discover that a powerful ghost inhabits the house.
Hunter Garth calls on Sam and Dean for help when he comes up against a Shojo, a Japanese creature that can only be seen and fought when the hunter is drunk.
When Lucifer pays Sam another visit, he drives him to the brink, forcing Sam to enter a mental hospital. Fearing for his brother's life, Dean takes matters into his own hands, calling upon every hunter he knows. He receives the name of a healer from one hunter, only to find a familiar face waiting for him.
A ballerina is killed by a pair of cursed dancing shoes, and Dean starts to fall victim to the same curse. However, that's the least of the brothers' concerns when they discover that the store where the shoes were sold has been bought out by Leviathans.
Sam and Dean return to follow up on an old case, the exorcism of a demon from a postal worker, when they discover that the demon has returned and is killing women, just like it did four years ago.
The brothers return to Kansas to investigate a children's pizza parlor that is connected to the death of several parents whose children all attended parties there. While Dean confronts the individual responsible, Sam has to deal with his worst fear: clowns.
Dean meets an intriguing woman at a bar while investigating attacks where the victims were branded with a strange symbol after their hands and feet were cut off.
While trying to rescue Dean, who has been thrown back into 1944 by the God of Time and must deal with Eliot Ness, Sam deals with the unexpected return of an old friend.
When Sam teams up with a familiar face, Dean is forced to team up with a laid-back hunter, Garth, and ends up working at cross purposes to his brother.
An angry ghost goes after mediums in Lily Dale, the most psychic town in America, and the brothers have to figure out who the next victim will be from a population filled with nothing but psychics.
Two Leviathans take on the form of Sam and Dean and frame them for a series of murders. While the brothers take refuge with a surveillance expert, Bobby tries to figure out how to kill the Leviathans and clear the Winchester brothers' names.
Sam and Dean deal with a witch who is using her powers to terrorize a small town. They soon discover that she is taking out her anger with her husband, who she discovered was having an affair.
The Egyptian god Osiris wreaks a bloody trail of deaths as he tries and executes anyone guilty of past mistakes. Sam is forced to defend his brother when Osiris targets Dean for his guilt over all the things he's believed he's done in his life... and calls Jo as a witness.
The Leviathan possession of Castiel has devastating consequences which leads Sam, Dean and Bobby back to Sioux Falls, Meanwhile Sam puts himself and Dean in danger as he begins to crack under intense pressure from Lucifer's mind games.
Castiel spares Bobby and the Winchesters and goes on his way to set right the wrongs of the world. However, when the brothers try to bind Death and use him to stop the new God, they discover that their former ally is one step ahead of them.