All those on Ravolox are in exponentially greater peril than anyone can comprehend. If anything in the entire universe is to survive, it may come down to the Doctor arguing against machine logic over the value of life.
Quest roles:
Roger Brierley(Drathro (voice)), Tom Chadbon(Merdeen), Tony Selby(Glitz), Joan Sims(Katryca), Adam Blackwood(Balazar), Glen Murphy(Dibber), Lynda Bellingham(The Inquisitor), Michael Jayston(The Valeyard)