The Doctor returns to Peladon fifty years after his last visit, to find Queen Thalira, daughter of the late King Peladon, on the throne. A tense labour dispute between Pel nobility and miners is worsened when apparitions of their deity Aggedor attack and kill several miners. The Galactic Federation desperately needs trisilicate for its war against Galaxy 5 and sends in brutal Ice Warrior troopers to ensure production. The Doctor discovers a devious plot at the heart of Aggedor's appearances.
The planet Peladon has applied to join the Galactic Federation, and The Doctor is mistaken for the chairman of the committee sent to assess its application, while Jo is taken for an Earth princess, with the mythical curse of Aggedor apparently striking chancellor Torbis dead, The Doctor must discover who is desperate to stop Peladon joining, but soon he is sentenced to death and his only Allies seem to be Jo and the Ice Warrior Delegates.
The TARDIS lands in a space museum on Earth in the late 21st century, where the Second Doctor, Jamie and Zoe learn that contact has been lost between Earth and the Moon. In this era, instant travel — T-Mat — has revolutionised the Earth. Its people have lost interest in space travel. The Doctor and his companions travel to the Moon in an old-style rocket and reach the Moonbase, control centre for T-Mat, only to find a squad of Ice Warriors have commandeered the base and plan to use the T-Mat network to their advantage.
