Sam and Dean have spent the last seven years battling the things that go bump in the night. Over the years, with the help of fallen-angel Castiel, and the King of Hell, Crowley, the Winchesters have straddled the line between good and evil. Last season, the boys encountered their worst enemy yet, Leviathan, a seemingly unkillable foe that, in the end, left Dean and Castiel stranded in Purgatory and Sam alone. Although Castiel is nowhere to be found, Dean manages a seemingly impossible escape from Purgatory – but not alone. He’s returned with a mysterious comrade-in-arms whose reason for escape is more than Dean bargained for. Meanwhile, Sam finds himself reconciling the life he rediscovered with Dean’s sudden reappearance. As the boys struggle with their unexpected reunion, they make a shocking discovery that could lead them on a deeply personal mission to settle old scores.