When their father goes missing while hunting supernatural creatures, brothers Sam and Dean Winchester set out to find him and battle the demons, spirits, and monsters they encounter along the way.
The Winchesters deal with the aftermath of the car crash which leaves the life of one of them hanging in the balance. John takes drastic measures to save his sons, but his actions have a profound effect on Sam and Dean.
As the Winchester brothers prepare to go on the hunt for the numerous creatures that escaped the Devil's Gate, Sam struggles to accept the sacrifice Dean made for him and the horrifying fate that awaits his brother in one year.
In season 4, Sam tries to do everything to save his brother. When Dean is freed from hell, he has no memory of how and why he went there and how he got out of there, and tries to solve the mystery with his brother.
With the apocalypse upon them, the trust between the brothers is broken as Dean struggles to come to terms with Sam's actions. The brothers discover that they have a larger role to play in the apocalypse as both angels and demons seek to use them as weapons.
Dean's peaceful life is shattered when he learns that Sam has made it back, but he soon comes to discover that there is something very wrong with his brother. The brothers are joined by their maternal grandfather, who is keeping a dark secret from them.
Castiel goes crazy with power after absorbing the souls of Purgatory, but some of the entities that have been unleashed prove too powerful for him to control, putting the world at risk. Sam is driven to the brink by a taunting Lucifer who forces him to face traumatizing memories of Hell.
Brothers Dean and Sam resume their journey of fighting all evil supernatural beings, as they begin a fight against Crowley to find the Demon Tablet and lock the Gates of Hell.
With Crowley and Abaddon clashing over control of Hell, Sam and Dean struggle to deal with the effects of their war, as well as the numerous fallen angels who have taken to possessing human bodies to survive.
Dean's transformation into a demon leaves Sam reeling. The Mark of Cain continues to affect Dean, leaving Castiel to seek help from Metatron.
Sam and Dean continue their battle against dark forces, and in this season they face a biblical dark being from ancient times, which wreaks havoc on land, and between the two brothers.
As the British Men of Letters continue plotting against the Winchesters, Sam and Dean deal with the return of their mother as well as the havoc that Lucifer is wreaking upon the world.
The Winchester brothers find themselves at odds after they take in Lucifer's son Jack, with Sam advocating for Jack while Dean plans to kill him to prevent him from hurting anyone.
Sam recruits the help of everyone trying to track down Dean. At the same time, Castiel might be on his tail after meeting with an unreliable source.
As the apocalypse looms closer, Sam and Dean Winchester set out on a journey to bring Chuck down and save humanity as evil souls roam the Earth after the gates of Hell were thrown open.