Ten-year-old Jerry Ronden is a walking nightmare who can make grown men cry. He sets off firecrackers in his parents' bed, deploys stink bombs in his own house, and soaps the aisle of the school bus. But his mischief making days are numbered. He discovers a window beneath his mum's washing line. Eyes glitter behind the window, and a voice calls to Jerry.

He doesn't have to wonder long who could be speaking to him. After a day full of his antics at school, the monsters climb out of the window and try to kidnap Jerry and drag him underground. Terrified, Jerry screams he will be good forever. The monsters run away, unable to stand being around a good child. Jerry now knows the monsters only come after children who behave like monsters themselves. They kidnap misbehaving kids and pull them underground, locking them in cages and feeding them until they decide the little troublemakers are ready to be eaten. This doesn't sound like a bright future to Jerry, so he tries very hard to improve his behavior.

Eventually, he just can't do it anymore. In a relapse, he steals a lollipop. As the monsters drag a struggling Jerry to the window in the ground, he knows it's all over - he doesn't deserve to be saved, and his parents probably don't love him anyway. But Mr and Mrs Ronden explode out of the family home, armed with an encyclopaedia and a rolling pin, ready to beat the monsters into submission.

When Mrs Ronden smashes the window, the monsters can't survive. They collapse into dust, and Jerry is saved. Jerry tells his parents he's sorry for his awful behavior, and they tell him they feel like they've been given a second chance too - a chance to love Jerry better.