Far in the distant future, Earth has become uninhabitable, forcing mankind to colonise first Mars, and then Pluto... No longer the coldest planet in the solar system, Pluto is now warmed by a series of artificial suns. But access to the sunlight is limited to a select few... The majority of the citizens of the vast Megropolis cities are being overworked and overtaxed by the ruling elite, led by the Gatherer, and the sinister Collector.

The Doctor, Leela and K9 arrive, and discover that all is not well on Pluto. The human population is being totally exploited, whilst deep in the Undercity, a small band of rebels seeks to overthrow the mysterious 'Company' that controls all aspects of everyday life.

As the situation gets more desperate, the Doctor is forced to fight the oppression of the evil corporate rulers of Pluto. And their taxes...!