The Cybermen have launched their deadly megatron bomb which will destroy all life on Earth unless the Doctor can deactivate the homing signal.
Quest roles:
Nicholas Courtney(Brig. Lethbridge-Stewart), Kevin Stoney(Tyrum), Terry Walsh(Doran (uncredited)), Pat Gorman(Pilot), John Levene(Sergeant Benton), Sally Faulkner(Isobel Watkins), Peter Halliday(Soldier), Charles Finch(Cyberman), John Spradbury(Cyberman), Clifford Earl(Major Branwell), Norman Hartley(Sergeant Peters), Ralph Carrigan(Cyberman), Robert Sidaway(Captain Turner), Richard King(Cyberman), Peter Thornton(Cyberman)