Years ago, Sam (Jared Padalecki) and Dean Winchester (Jensen Ackles) lost their mother to a mysterious and demonic supernatural force. Subsequently, their father raised them to be soldiers, teaching them about the paranormal evil that lives in dark corners and on the back roads of America. And he taught them how to kill it. This haunting series follows the Winchester brothers as they travel the lonely and mysterious back roads of the country in their '67 Chevy Impala, hunting down every evil supernatural force they encounter along the way. At the start of the fourth season, Dean has been freed from Hell, but he can't remember how or why, or what happened while he was there. It soon becomes clear that Sam has secrets of his own, including what happened in the four months Dean was gone. 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. If Sam and Dean can't stop it, it could mean the Apocalypse...