Ghosts of children Bobby couldn't save cripple him with guilt and Sam and Dean must save him. However, they must also ignore the spirits of Meg and Agent Hendricksen, who have come back to accuse the brothers of failing them.
Sam and Dean investigate the mysterious deaths of several men who seemingly died of fright. Dean becomes infected with it starting as anxiety then leading to a full-blown terror which ends in death. Sam and Bobby race against time to save Dean.
Sam, Dean, and Ruby look for Anna who hears the voices of angels. When Ruby seemingly betrays the brothers and leaves with Anna, Sam enlightens Dean on how Ruby saved Sam's life while Dean was in Hell.
Sam and Dean seek help from Pamela, who sends the brothers to the spiritual realm. They discover Alastair attempting to break the seal causing mayhem in the mortal world by stopping death from occurring in a small town.
Dean and Sam now lead ordinary lives. Dean works in the corporate world at the Sandover Bridge & Iron Company along with Sam who works as a Tech Support. Both have no idea who the other is until their colleagues start killing themselves.
Sam and Dean come across a series of novels called Supernatural depicting their lives as demon hunters in detail. The brothers meet the author of the comics, Chuck, who explains he has visions of Sam and Dean in action then puts their adventures in his novels.
Sam and Dean are on a hunting trip when they receive a call from an Adam Milligan, who is trying to find John Winchester. They discover that Adam was conceived 19 years ago when his mother fell in love with John Winchester.
Dean has a dream about Castiel asking to meet him in private. Sam and Dean are shocked to discover Castiel's human host, Jimmy, is back in control. Jimmy wants his life back but Sam and Dean believe he is in danger.
Sam is locked in Bobby's panic room to cleanse his body from demon blood. However, after several seals are broken Bobby wants to set Sam free to help stop the Apocalypse and Dean seeks out Castiel for help.