Every town on Discworld knows the stories about rats and pipers, and Maurice - a street wise 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 someones playing a different tune. Now Maurice and his rats must learn a new concept: evil...

When Charles Townsend's agency expands abroad, two established Angels team with a new recruit to fend off enemies from securing a revolutionary device.