The deep-space trading post of Iceworld, the far future. The Doctor, Mel, their old friend Glitz and time-lost waitress Ace go in search of a fabulous treasure, supposedly guarded by a fire-breathing dragon. But what is the link between the treasure and Iceworld's proprietor, the frosty Mr Kane?

While Mel and Ace run from Glitz's former crewmen (whom he sold to Kane), officers Belazs and Kracauer conspire to overthrow Kane. The Doctor, meanwhile, discovers there really is a dragon in the ice caverns, which turns out to be a bio-mechanoid with a very interesting function.

At last learning the location of the missing key to his spaceship, Kane has the dragon hunted down and Iceworld brutally purged of all visitors; but, the Doctor, visiting the Ice Garden, learns something significant that will put the chagrin on Kane's grand plans for home world vengeance.