Castriel investigates the mass slaughter of angels and finds a lone survivor... and an old friend. Meanwhile, Sam and Dean capture Gadreel, and Metatron begins the ending of his story.

After attacking Gadreel, Dean leaves with Crowley to track down Metatron and kill him. Meanwhile, Gadreel takes Castiel into Heaven to try and break Metatron's connection to the angel tablet, stripping him of his powers.

After the massacre at the ranch, Dean, Sam, and Castiel double their efforts to find a cure for the Mark of Cain but there is nothing in the lore that can help them. Desperate, Castiel comes up with an idea that Sam deems the "single worst idea I've ever heard." Meanwhile, Rowena continues to plot against Crowley, and Castiel tries to mend his relationship with Claire who is plotting revenge against Dean for killing her friend.