Twenty-three years ago, Sam and Dean Winchester lost their mother to a mysterious and demonic supernatural force.

Subsequently, their father raised them to be soldiers. He taught them about the paranormal evil that lives in the dark corners and on the back roads of America... and he taught them how to kill it.

With their father gone, Sam and Dean are now facing an all-out demonic war. As they work to stem the rising tide of demonic activity, they continue to travel the country, battling the supernatural - changelings, cursed objects, vampires, witches, malevolent spirits, even a very un-merry Anti-Claus - wherever they go.

Season four begins four months where the third season left off, and Dean wakes up in a pine box. He's been freed from Hell, but how? And by what? Dean and Sam reunite and, as they puzzle out Dean's resurrection, they hit the road, battling the supernatural wherever they go. They encounter malevolent spirits, the terrifying demonic origin of Halloween, Dracula himself and even a drunk, heavily armed 7-foot-tall teddy bear. Meanwhile, the brothers contend with new mysteries.

What happened to Dean while he was in Hell, and why can't he remember it? It soon becomes clear that Sam is hiding secrets of his own, starting with the truth of what happened during the four months Dean was gone. As the brothers answer these questions, they also face a dire threat. There are whispers that a certain demon will soon be freed from his prison deep in Hell: Lucifer. And if Sam and Dean can't stop it - if Lucifer walks free - he'll bring on the Apocalypse ...