Sam and Dean spent their lives on the road, battling every kind of supernatural threat. A year after the Apocalypse, Dean's past inevitably catches up to him when Sam, mysteriously freed from his cage in hell, needs his brother to rejoin the fight because a new threat is rising in the dark corners and backwoods of America.
In fourth season, Dean has been freed from Hell, but he can't remember how or why, or what happened while he was there. As the brothers answer these questions, they also face a dire threat. There are whispers that an evil demon will soon be freed from its prison.