Dean returns from Purgatory, one year after the fight with the Leviathans. After reuniting with Sam, they find out that Kevin escaped Crowley with another Word of God that may hold the key to closing the gates of Hell forever.
Dean assists the vampire, Benny, who helped him escape from Purgatory. Together they go after the nest led by the vampire that bit Benny. Sam thinks back to his life before Dean returned.
Sam and Dean team up with Garth, who has taken over Bobby's job, as they hunt down a Specter that's possessing innocent people who have a grudge against someone.
Crowley has kidnapped Kevin and the rest of the prophets that are able to read the Word of God. Castiel mysteriously returns from Purgatory and helps Sam and Dean rescue Kevin.
Castiel decides to become a hunter, like Sam and Dean. But his first day on the job is a doozy when they investigate a series of murders caused by old cartoon gags. Meanwhile, Sam thinks back to his first time meeting Amelia's father.
Sam and Dean's grandfather, Henry Winchester, arrives by time travel, claiming that he has something to protect from an Abaddon that is hot on his trail.
While searching for Kevin, again, Charlie joins up with Sam and Dean as they track down a creature that's been liquefying its victims. Plus, a new side of Charlie is revealed.
Sam and Dean search for the Word's author, Metatron. Castiel tries to protect the angel tablet. Kevin tries to solve the third trial under Crowley's supervision.
Sam and Dean try to figure out how to cure a demon. Crowley starts killing victims that Sam and Dean have saved from previous jobs. Castiel and Metatron begin the trials to close the gates to Heaven.
Sam and Dean capture Crowley to finish the trials and close the gates of Hell. Castiel and Metatron continue the trials to close the gates of Heaven. Sam is left with a huge decision.