Mr. Wilson's ever-present annoyance comes in the form of one mischievous kid named Dennis. But he'll need Dennis's tricks to uncover a collection of gold coins that go missing when a shady drifter named Switchblade Sam comes to town. When his parents must go out of town on business, Dennis stays with Mr. and Mrs. Wilson. He is driving Mr. Wilson crazy, but he is just trying to be helpful, even to the thief who has arrived in town.