Rats! They're everywhere: in the breadbins, dancing across tabletops, stealing pies from under the cooks' noses. So what does every town need? A good piper to lure them away.

That's where Maurice comes in. But he's only a cat (though one that talks), so although he has the ideas, he needs rats and someone to play the pipe. Who better than the kid to play the pipe? And Dangerous Beans. And Peaches. And Hamnpork (who doesn't really like what's been happening since The Change; all a rat leader really needs is to be big and stroppy, thinking is just not his thing). And Darktan. And Sardines. And all the others in the Clan.

Then they arrive in Bad Blintz, which is suffering from a plague of rats, and find there are NO rats anywhere (though the two resident rat catchers seem to have plenty of tails to show, at 50 pence per tail).

Someone else has had ideas, and Maurice is not pleased.