Supernatural — Episode 16: ...And Then There Were None

You are watching the episode ...And Then There Were None Eve, the Mother of All, unleashes a new monster upon the world: a black worm-slug that can enter the brain and force people to kill. Sam and Dean join forces with Bobby and Rufus and track it to a cannery, only to discover that Gwen and Samuel are also there looking for the monster... and none of them know who the monster is inside.