Colin Baker (The Doctor), India Fisher (Charley Pollard), Philip Madoc (Rag Cobden), Matthew Burgess (Ned Gillespie), Susan Brown (Eleanor Harvey), Glynn Sweet (Professor Lyle Woodruff), Ian Brooker (Romilly), Andrew Dickens (Security), Nicholas Briggs (Krotons)
The dead planet Onyakis is being plundered by the last survivors of the human race, and their leader, Commander Cobden, will stop at nothing to get what he wants. Already there are rumours of those who stand against him mysteriously disappearing. But when the Doctor and Charley find themselves on the side of those trying to expose Cobden, they discover something far more sinister.
Deep in the mines of Onyakis, alien technology is reactivating. Power is flowing. Something is forming in the darkness...