The Doctor - Tom Baker
Leela - Louise Jameson
Nucleus Voice / K9 Voice - John Leeson
Lowe - Michael Sheard
Safran - Brian Grellis
Silvey - Jay Neill
Meeker - Edmund Pegge
Crewman - Anthony Rowlands
Professor Marius - Frederick Jaeger
Parsons - Roy Herrick
Marius' Nurse - Elizabeth Norman
Reception Nurse - Neil Curran
Opthalmologist - Jim McManus
Cruikshank - Roderick Smith
Hedges - Kenneth Waller
Medic - Pat Gorman
Nucleus - John Scott Martin