Iceworld. An intergalactic trading post, ruled by the power-hungry Kane. Now his dream of total power is near to realization with his acquisation of a band of mercenaries from the infamous Glitz in part payment of his debts. For "Cryosleep" will render the men utterly in his power. Meanwhile, Glitz still owes the balance of the debt and looks to Iceworld's mythical dragon and the Dragonfire - the treasure it reputedly guards - to solve his problems at last.

Intrigued by the legend of the Dragonfire, the Doctor, Mel and young Earth girl, Ace, accompany Glitz - unaware that they are being followed by Kane's mercenaries. For the psychotic ruler believes that with the Dragonfire in his possession he can avenge the rulers of his home-planet who banished his long-dead partner 3,000 years ago.

And so it seems that beneath Iceworld's superficial civility lies a frozen core of corruption and the Doctor has embarked on something far more sinister than a mere treasure hunt...