Returning to the medieval planet Peladon (50 years after "The Curse of Peladon") The Doctor and Sarah find King Peladon's daughter Queen Thalira has inherited the throne and the galactic Federation is at war with Galaxy Five and The Federation requires the mineral Trisilicate that will end the war. Only to discover the miners led by the mad rebel Ettis are rebelling and refusing to work, as the ghost of the loyal best Aggedor is frightening and killing off Miners, only to discover the ghost of Aggedor is a holographic projection and the culprits are a task-force of renegade Ice Warriors led by Commander Azaxyr and traitorous federation mining engineer Eckersley who have betrayed the Federation to Galaxy Five.