Doctor and Leela land on the planet Kaldor, home of the Sandminer crew that they recently saved from the dreaded Robots of Death.Intrigue abounds still further on the homeworld. The twisted genius that perverted the robots from their function to serve man, the late Taren Kapel, has become the deity of a cult that is causing chaos. Leda finds herself caught up in their mayhem while the Doctor learns that the survivors of the original sandminer crew are being killed off one by one.