Castiel doesn't hug Sam, Dean and Bobby but warns them not to interfere in his business. Assuming his new role as God, Castiel sets out to right some of the wrongs in the world. Dean decides they should bind Death and order him to stop Castiel, but the former angel is one step ahead of them, leaving Dean to face a very angry Death. Meanwhile Sam struggles to deal with the broken wall in his head.
The broken wall in Sam's head causes him to have hallucinations, and he has difficulty discerning what's real and what's not. Bobby worries that Dean is beginning to stumble under the weight of fighting and keeping an eye on Sam.
Dean is furious after Sam disappears to follow a lead on a case with clues that are identical to a case Sam solved as a kid. The demon turns out to be Amy, who has been killing low-life thugs and taking their brains for dinner - the same demon Sam found as a kid.
Sam and Dean investigate a string of gruesome murders and discover the Egyptian god Osiris is behind the deaths. The vengeful god is putting people on trial for their past mistakes and killing them if found guilty. Osiris hones in on Dean's guilt and decides he's the next to stand trial. Sam steps in as Dean's lawyer, but both brothers are unprepared when Osiris calls an unexpected witness Jo.
Sam and Dean meet Maggie Stark, a witch who has unleashed her wrath on a small town, resulting in numerous deaths. Sam and Dean track down her husband, Donald, to see if he can help. Donald tells the brothers that Maggie is mad at him for having an affair and is taking it out on the townspeople.
Sam and Dean are once again on the FBI's "Most Wanted" list when two Leviathans clone the brothers and go on a killing spree. The subject of a nationwide manhunt, Sam and Dean need to drop off the grid so Bobby sends them to Frank Deveraux, a quirky surveillance expert, for help. Meanwhile, Bobby continues to search for a way to hug the Levianthans, or at least slow them down, so the real Winchesters can stop their evil doppelgangers.
Sam and Dean investigate the gruesome murders of resident mediums in Lily Dale, the most "psychic" town in America. They discover that an angry spirit is killing off the psychics one by one, but in a town full of people who claim to be summoning spirits, they have a little trouble identifying the medium controlling the ghost.
During the brothers' annual pilgrimage to Las Vegas, Sam makes a life-shattering decision and takes on a new partner. Dean soon finds a new hunter as a partner, but the Winchesters meet again when they end up investigating the same case.
Sam, Dean, and Bobby become actual hunters, in the true sense of the word, when they set up camp in a New Jersey state park to track a creature that has been attacking people in the woods. The townsfolk claim it is the real Jersey Devil. Meanwhile, Dean is beyond thrilled to find a Biggerson's restaurant in town, but is devastated when he discovers the restaurant's special sandwich seems to be making people crazy.
As Sam and Dean race the clock on a high-stakes mission, Bobby seeks the help of an unlikely old friend to solve one of the most personal cases of his life.
Still reeling after what happened to Bobby, Dean becomes dangerously obsessed over finding a way to take down Dick Roman. Meanwhile, Sam decides to help a teenage girl look for her father, a hunter who has gone missing. Sam traces his last steps to a truck stop where the help turns out not to be so friendly.
Sam and Dean tangle with the God of Time, who sends Dean back to 1944, where he is immediately arrested by none other than the one and only Eliot Ness. While trying to figure out how to retrieve his brother, Sam is surprised by the reappearance of an old friend.
Sam and Dean investigate a case where the victims' hands and feet have been severed and each have been branded with a strange symbol. While Sam does some research at a local university, Dean heads to one of his favorite places to investigate - the town bar. Dean strikes up a conversation with a local named Lydia, and the two go back to her place. Sam discovers the symbol on the bodies is a sign of Amazon warriors.
Sam and Dean investigate strange happenings in a town where childhood fears are coming to life. To Sam's horror his childhood fear of clowns manifests in a very unhappy and traumatic way which in turn leads to Dean's childhood fear, losing his brother.
Four years ago, Sam and Dean helped a woman named Nora exorcise a demon that was systematically killing women in a small town. They managed to save a postal worker, Jeffrey, while vanquishing the demon, but now it seems the black-eyed monster has reared his ugly head and returned for a second helping. The brothers visit Jeffrey, who has been locked in a psych ward since the incident, to see if he can remember any of the demon's plans while he was possessed.
The brothers investigate several cases of cursed antiques turning up in Portland, but soon discover something far more sinister when they learn that the Leviathans are buying up real estate in the area. Meanwhile, Sam is still plagued by Lucifer's voice in his head.
Lucifer drives Sam to the breaking point and Sam ends up in a mental hospital. Desperate to save his brother, Dean calls every hunter he knows for help. One of the hunters gives him the name of a healer who turns out to have a very familiar face.
Dean's one-time hunting partner, Garth, calls him in when he runs up against an invisible monster that disembowels its victims. Garth and the Winchesters soon discover that someone has invoked a shojo, an alcohol spirit that someone can only see when they're drunk. Meanwhile, the Winchesters consider the possibility that Bobby's spirit is trying to contact them.
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.
Dick Roman acquires Frank's hard drive that contains sensitive information about the Winchesters and gives it to an unsuspecting brilliant hacker named Charlie telling her she has 3 days to crack the encryptionl or she is fired. Sam and Dean are tipped off that Dick has the hard drive and race to get to Charlie before she breaks the code. Meanwhile, Bobby tries to help the brothers, but his rage towards Dick for killing him starts to get in the way.
Meg calls Dean and Sam and tells them Castiel is awake and talking. Meanwhile, a teenager named Kevin gets hit by a bolt of lightening and is turned into a reluctant prophet. Sam and Dean believe Kevin holds the key to defeating the Leviathans but must fight off two Archangels who want him for their own purposes.
In order to defeat Dick Roman and the Leviathans, Sam and Dean must locate three key items. Castiel helps with one but for the last objects, the Winchesters must face two of their strongest opponents - an Alpha and Crowley. Meanwhile, Bobby tries out a new ghost trick that ends up being very dangerous.
As Dick Roman prepares to make his move and turn the U.S. into a slaughterhouse, Sam and Dean attempt to assemble the weapon necessary to stop him. However, when Castiel refuses to fight, the Prophet Kevin is captured, Crowley joins the other side, and Bobby goes berserk, everything looks hopeless for the Winchesters.