The planet Peladon, some time in the future. The Doctor and Sarah arrive on the planet Peladon 50 years after "The Curse of Peladon" They find King Peladon's daughter, Queen Thalira has inherited the throne. The Galactic Federation is at war with Galaxy Five and needs the mineral Trisilicate in order to bring about an end to the war. It seems the Ghost of Aggedor has been sighted and is blamed for killing of miners, which hampers the acquisition of the much needed Trisilicate.
Elenco: William Hartnell , Patrick Troughton , Jon Pertwee , Tom Baker , Peter Davison , Colin Baker , Sylvester McCoy .