Dean is a demon and running amuck with Crowley while Sam tries to figure out what happened to his brother. Meanwhile, Castiel is dealing with his fading grace.

Crowley is worried that Dean, driven by the mark, is getting out of control. Sam struggles to escape from Cole. Hannah tries to convince Metatron to give Castiel his grace back.

Sam and Dean discover a group of witches on a gone wild trip and attempt to stop them.

Despite Dean's directive to forget about looking for a cure for the Mark of Cain, Sam continues to do research. Dean suspects Sam is hiding something but decides to focus on a new murder case where they run into Cole. The three team up and learn a Khan worm is infecting men and turning them into murderers. Unfortunately, the worm makes its way into Cole.