Picking up where the finale left off, Sam and Dean must deal with the Darkness that has been unleashed. Castiel deals with the effects of Rowena’s spell and recalls his brutal battle with Crowley.

Dean helps Jenna, the deputy he met after the Darkness fell, get back home safely and then sets off to help Sam deal with a town infected by a mysterious and deadly gas. However, when Jenna falls into dangerous hands, she calls Dean for help and Sam tells him to go back to her. Unfortunately for Sam, he isn't able to handle the townspeople turned monsters as easily as he thought.