Season fifteen kicks off where season fourteen finished: Gothic horror. The TARDIS materialises in a lighthouse on an isolated piece of shoreline just after a mysterious light has been seen falling from the sky and one of the lighthouse-keepers is found electrocuted. The Rutans are described by the Doctor as being the ancient and implacable enemies of the Sontarans, who have appeared multiple times in the show's history; this is the only appearance so far of the Rutans.