When Sam and Dean receive a distressing video message from Kevin Tran, they set out trying to uncover the third trial. The boys make a discovery that sends them to a casino in Colorado where they find a mysterious recluse who may be able to fill in the holes in Kevin’s research. Meanwhile, Castiel tries to elude Naomi and the angels hunting him.

Sam and Dean are reunited with Castiel as they are digging through the Men of Letters' files. They stumble upon an film which could be the key to completing the third trial. Metatron enlists Cass to mull over problems at home.

With Crowley poised to undo all the good they’ve ever done as hunters, Sam and Dean find themselves cornered. But with Kevin's help, the Winchesters ready themselves for one last play against the King of Hell. Metatron initiates a plan with Castiel to take on Naomi and the bureaucracy of Heaven.

The angels are embroiled in a bloody civil war, and Castiel is swept up in the conflict. Meanwhile, Dean realizes that Ezekiel is not who he claims to be and tries to warn Sam with dire results.

Dean and Castiel make a deal with Crowley in order to contact Sam's consciousness so he can expel the angel Gadreel from his body. However, Abaddon is hot on their trail and Crowley has plans of his own.

Castiel 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 an angel carries out a suicide attack on an ice cream shop to kill one angel from another faction. Sam and Dean investigate and discover that the target was one of Metatron's angels and that Castiel may be responsible.

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.

Crowley is worried that Dean, driven by the mark, is getting out of control. Sam struggles to escape from Cole. Hannah tries to convince Metatron to give Castiel his grace back.

After the massacre at the ranch, Dean, Sam, and Castiel double their efforts to find a cure for the Mark of Cain. Desperate, Castiel comes up with an idea that Sam deems the single worst idea he's ever heard. Meanwhile, Rowena continues to plot against Crowley.

Sam and Castiel follow up on a lead about the Mark of Cain. Dean and Rowena meet.

Charlie calls Sam and Dean to tell them she found the Book of the Dead which could help remove the Mark of Cain. The Winchesters race to her after she tells them she’s been shot by a man named Jacob Styne who says the book belongs to his family and he won’t rest until he gets it back. Castiel and Metatron take a road trip to find Castiel’s grace but they hit a couple road bumps along the way.

Amara shows Dean how she’s torturing Lucifer. Worried for Castiel, Dean and Sam come up with a plan to rescue him from Amara’s clutches.