The TARDIS lands on the Ood-Sphere in the year 4126. Here, human profiteers have subjugated the Ood: the gentle creatures are forced into servitude and sold across the galaxy as the perfect slaves. But now, some are fighting back. Their eyes turn red as they throw off their chains and kill their oppressors...

The Doctor and Donna soon learn that the planet of the Ood holds cruel and awesome secrets. As they battle for justice and survival, the fate of the entire Ood race hangs in the balance. Will the outcome be salvation - or extinction?