A survey team of eight men from the mighty Morestran Empire lands on Zeta Minor, a remote planet on the fringes of the universe. Before their expedition is over, seven of the men are mysteriously and horrifically murdered.

A distress signal brings the Doctor to the planet -but his good intentions are not appreciated. The commander of a Morestran rescue party, sent to investigate the disappearance of the survey team, is convinced the Doctor is the killer.