Harker and the Doctor retrieve Ben's body and the Time Lord deduces it has been used as an anatomy lesson for an alien life form. He determines that their best protection is to secure the lighthouse to keep the creature out. Reuben then disappears for a time and then reappears a changed man, which the others put down to shock, but the pattern of death now speeds up. Palmerdale is killed in the lamp room by a glowing alien presence on the outside of the lighthouse, and then Harker is killed when Reuben corners him in the boiler room. From the alien light emanating from Reuben it is clear he has become possessed or transformed by the alien creature. The Doctor finds Harker's body and then Reuben's own – the latter cold for some time – which means the creature in Reuben's form has chameleonic properties.