'Anything you do in the past changes the future. The tiniest little actions have huge consequences. You might tread on an ant now and it might entirely prevent someone from being born in the future.'

Rincewind, inept wizard and reluctant hero, has found himself magically stranded on the Discworld's last continent.

It's hot. It's dry. There was this thing once called The Wet, which no one believes in any more. Practically everything that's not poisonous is venomous. But it's the best bloody place in the world, all right?

And in a few days, it will die. The only thing standing between the last continent and wind-blown doom is Rincewind, and he can't even spell wizard. Still . . . no worries, eh?