While Ara tries to save Polly from being turned into a Fish Person and Ben and Jamie try to escape from the mines, the Doctor discovers the full extent of Zaroff's plans.
Quest roles:
Anneke Wills(Polly), Michael Craze(Ben), Colin Jeavons(Damon), Joseph Fürst(Zaroff), Tom Watson(Ramo), Noel Johnson(Charles Grover M.P.), Catherine Howe(Ara), Graham Ashley(Overseer), Peter Stephens(Lolem)