S7, E22: In order to defeat Dick Roman and the Leviathans, Sam and Dean must locate three key items. Castiel helps with one but for the last objects, the Winchesters must face two of their strongest opponents - an Alpha (guest star RICK WORTHY) and Crowley (guest star Mark Sheppard). Meanwhile, Bobby (guest star Jim Beaver) tries out a new ghost trick that ends up being very dangerous.