The Doctor and Adric learn from the wizened Keeper of Traken that a great evil has come to his planet in the form of a Melkur - a calcified statue. The Keeper of Traken is nearing the end of his reign and seeks the Doctor's help in preventing the evil from taking control of the bioelectronic source that is the keystone of the Traken Union's civilisation.
Tom Baker
The Doctor
Matthew Waterhouse
Adric
Sarah Sutton
Nyssa
Geoffrey Beevers
Melkur (voice) / The Master
Anthony Ainley
Tremas / The Master
Sheila Ruskin
Kassia
Denis Carey
The Keeper
John Woodnutt
Seron
