Dean is a demon and running amuck with Crowley while Sam tries to figure out what happened to his brother. Meanwhile, Castiel is dealing with his diminishing grace.

In a black-and-white world reminiscent of classic horror flicks, the brothers tangle with a vampire, a werewolf and a mummy who are thinning the crowds at a quaint Oktoberfest.

Diggle and Felicity travel to the island of Lian Yu in search of Oliver, who left Starling City after the devastation of The Undertaking and his failure to avert it….

Bellamy, Finn and Jasper head into Grounder territory to search for Octavia, as flashbacks show the siblings’ difficult childhood on the Ark. Meanwhile, Raven finds out about Clarke and Finn.