Investigating the appearance of the Voord on Earth, the Doctor, Liv and Helen follow a trail which takes them to the other side of the universe. There they discover a mysterious and almost deserted gothic city lost in space and time, in which the grotesque inhabitants are conducting a vile and inhumane experiment. The Doctor and his companions must hurry to save the lives of those in danger before the experiment is a success and the unimaginable consequences become all too real.