Arriving onboard a spaceship, the Eleventh Doctor and Amy Pond are soon attacked by a creature. It is referred to as "the Charonid" by the ship's only conscious crewmember, Cormac, who fires a stun pistol. The Charonid runs off. Cormac explains it knocked out all the other crew, but when the Doctor and Amy find the unmarked body of the pilot they are suspicious. The Doctor recalls the Charonid being body swappers and with the pilot having been stunned, he guesses that Cormac is the Caronid.