S10, E18: Charlie (Felicia Day) calls Sam and Dean to tell them she found the Book of the Dead, which might help remove the Mark of Cain. The Winchesters race to find her after she tells them she's been shot by a man named Jacob Styne (guest star Jeff Branson) who says the book belongs to his family and he won't rest until he gets it back. Castiel and Metatron (guest star Curtis Armstrong) take a road trip to find Castiel's grace... but they hit a couple road bumps along the way.