Great A'Tuin, the star turtle, who supports the weight of the Discworld, labours through the galactic night, the only creature in the entire universe that knows exactly where it is going. Philosophers have debated where this is - they are due to find out in about two months. And then they are really going to worry. As it moves towards a seemingly inevitable collision with a malevolent red star, the Discworld has only one possible saviour. Unfortunately, this happens to be the singularly inept and cowardly wizard called Rincewind, who was last seen falling off the edge of the world...