Sam and Dean try to convince Crowley to turn over the Horn of Joshua before destroying Lucifer--and Castiel--rather than after they use the Horn to defeat Amara. Meanwhile, an unexpected ally helps Amara heal from her injuries, and Lucifer makes the angels in Heaven an offer they can't refuse.

The brothers investigate a murder-suicide in Colorado that may be tied to Amara. Meanwhile, Metatron receives a request to edit a new book.