The Doctor and Jo arrive on the medieval planet Peladon, where the Doctor is mistaken for the Earth Delegate of the Galactic Federation and Jo is mistaken for a princess.

The Doctor is convinced the Ice Warriors are trying to sabotage the conference but his attempts to prove it see him accused of sacrilege.

The Doctor is sentenced to fight Grun to the death and his attempt to escape leads to an encounter with Aggedor.

Hepesh's plan has been exposed but he is still determined to prevent Peladon joining the Galactic Federation by leading a rebellion against the King.