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 . . .