One morning the townspeople of Dull-on-Sea wake to find that their town is overrun with rats. Big rats, small rats, fierce rats, hungry rats - it is an infestation! Just when everyone is at their wit's end, a nautical stranger who plays the pipe turns up and offers to get rid of the rodent problem - for a fee. Once that rats have gone, the greedy town councillors refuse to pay - so of course the piper pirate leads the children away. It's up to Matilda, Jim and Nugget to save them.