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

Sam and Dean reunite with Castiel. Digging through the Men of Letters' files, they stumble upon an undiscovered film which could be the key to the third trial. Metatron enlists Cass to mull over problems at home. Meanwhile, Crowley digs into Sam and Dean's past.

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 Winchester brothers bound into one last play against The Demon King. Metatron initiates a plan with Castiel to take on Naomi and the bureaucracy of Heaven.

The angels fight each other in 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 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.

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 a suicide angel takes out an ice cream shop to kill one enemy angel, Sam and Dean investigate and discover that the target was one of Metatron's angels... and that Castiel may be responsible. Meanwhile, Metatron tries to consolidate his hold over the angel factions with promises that he will restore them to Heaven.

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.

Crowley is worried about Dean getting out of control, giving him a target to feed the mark. Sam struggles to escape from Cole. Hannah tries to convince Metatron to give Castiel's grace back.

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.

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.