One morning the residents of Dull-on-Sea wake up to find their town is overrun -- with rats! Big rats, small rats, fierce rats, hungry rats. It's an infestation! Just when everyone is at their wits' end, a nautical stranger who plays the pipe turns up and offers to get rid of the rodent problem for a fee. But once the rats are gone, the greedy mayor of Dull-on-Sea refuses to pay -- so the Pirate Piper plays an enchanted tune and leads the children away. Can Jim, Matilda, and Nugget save their friends?