When a Dungeon Master is killed, Liv and Clive discover he was up to more than just playing in his mother’s basement. Meanwhile, Blaine’s experiment does not go as planned….

Barry enjoys the annual tradition of tree trimming and gift exchange with Joe and Iris. He gives Iris a touching gift, but the moment is interrupted by Eddie’s arrival.

The Flash goes up against Farooq aka Blackout, a metahuman who can harness electricity.

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