The Hogswatchnight yuletide season is disrupted by the evil deeds of the Auditors, who replace the red-suited Hogfather with a scythe-bearing demon, prompting the Unseen University wizards and their monster-bashing nanny to launch a rescue plan.

It's hard to grow up normally when Grandfather rides a white horse and wields a scythe - especially when you have to take over the family business, and everyone mistakes you for the Tooth Fairy. And especially when you have to face the new and addictive music that has entered Discworld.

Change is afoot in Ankh-Morpork - Discworld's first steam engine has arrived, and once again Moist von Lipwig finds himself with a new and challenging job.

IT'S A RAT-EAT-RAT WORLD . . . Every town on Discworld knows the stories about rats and pipers, and Maurice - a streetwise tomcat - leads a band of educated ratty friends (and a stupid kid) on a nice little earner. Piper plus rats equals lots and lots of money. Until they run across someone playing a different tune. Now he and his rats must learn a new concept: evil . . .