Tom Baker as The Doctor

Lalla Ward as Romana

David Brierly as K-9 (voice)

Christopher Neame as Skagra

Daniel Hill as Chris Parsons

Denis Carey as Professor Chronotis

Victoria Burgoyne as Clare Keightley

Gerald Campion as Wilkin

Shirley Dixon as The Ship (voice)

Derek Pollitt as Dr. Caldera

James Coombes as The Krargs (voice)

John Hallet as Police Constable

David Strong as Passenger

James Muir as Fisherman

Derek Suthern as Krarg

Barnaby Edwards as Krarg

Tim Bentinck as The Doctor (body double)

Toby Hadoke as Continuity Announcer (voice)