Guest Stars Nicholas Courtney as Alistair Gordon Lethbridge-Stewart Pat Gorman as Cyberman Peter Halliday as Packer Kevin Stoney as Tobias Vaughn Sally Faulkner as Isobel Robert Sidaway as Captain Turner James Thornhill as Sergeant Walters Edward Burnham as Professor Watkins Edward Dentith as Major-General Rutlidge Sheila Dunn voices Telephone Operator