"So, that's an Ice Warrior. Brings a whole new meaning to the concept of shell suits."
The Doctor is pursuing a master criminal. The trail leads to Peladon: a desolate world once home to a barbaric, feudal society. Now the Galactic Federation is attempting to bring prosperity and civilisation to the planet. But not all Peladonians support the changes, and when ancient relics are stolen from their Citadel, the representatives of the Federation are blamed. The Doctor suspects the Ice Warrior delegation, but before long the Time Lord himself is arrested for the crime — and sentenced to death.
Elsewhere, interplanetary mercenaries are bringing one of the galaxy's most evil artefacts to Peladon, apparently on the Doctor's instruction. Ace is pursuing a dangerous mission on another world and Bernice is getting friendly — perhaps too friendly — with the Ice Warriors she has studied for so long.
The players are making the final moves in a devious and lethal plan — but for once it isn't the Doctor's.