250,000 years' worth of junk floating in deep space, home to the shipwrecked Sittuun, the carnivorous Sollogs, and worst of all - the Humans. The Doctor and Amy arrive on this terrifying world in the middle of an all-out frontier war between Sittuun and Humans, and the countdown has already started. There's a comet in the sky, and it's on a collision course with the Gyre... .