In the episode, Cyd's dog, Diesel, accidentally consumes Barry's invented wolf-serum and becomes a half-wolf monster going after both Cyd and Shelby. During the encounter, Diesel hurls the serum at Cyd. The protagonists successfully travel back in time to prevent Diesel from getting into the serum, but during the preparation for the school's Halloween party, Cyd feels the effects of the serum and turns into a werewolf.