On this week's episode of Supernatural…
Sam and Dean investigate a series of killings that lead them to a witch couple, Don and Maggie Stark, with marital problems.
Sam and Dean stop the two from killing each other and counsel them back together.
The Leviathan that has been hunting them shows up, but Don casts a spell on the Leviathan and saves the brothers. He also saves them from being killed by Maggie.
Sam questions Dean and his repressed guilt, as well as his drinking.
The two drive away with the captured Leviathan.