The Duke of Dulwich is in distress—several reports are coming in that the city is beginning to be overrun by a plague of rats. Naturally he has killed off all witnesses, but daily the problem is becoming more obvious. His corrupt council, led by the hapless ex-wizard Tambor, has no solutions. He must send for mercenaries to rid his city of the rampant rodents.

Heralds ride out from every gate, each hoping to bring back the savior of the city. Part-time herald, full-time thief, and grandson to Tambour, Jimmy Quickstint is the lucky man—falling haphazardly upon the skills of Diek Wustapha—a charmer—recently inhabited by magic and suddenly irresistible to girls, sheep—and rats.

Diek fulfills his task and is promised $500 for his troubles. But once the rats have gone, the council reneges on their deal. Full of anger (and magic), Diek charms the children of Dulwich out of the city, playing on his mouth organ, where he disappears into the caves ad woodland of the surrounding area.

The Duke is now in despair and has to resort to mercenaries to track him down. These include Groan Teethgrit (a man-mountain with more fingers than brain cells), Gordo Goldaxe (a dwarf who takes offence at people looking down on him) and Jimmy Quickstint (the only thief in history to go into a house with more than he came out with). And it's not looking good.