Harry Crumb is a bumbling and inept private investigator who is hired to solve the kidnapping of a young heiress which he's not expected to solve because his employer is the mastermind behind the kidnapping.

When his brother asks him to look after his young son, Clifford, Martin Daniels agrees, taking the boy into his home and introducing him to his future wife, Sarah. Clifford is fixated on the idea of visiting a famed theme park, and Martin, an engineer who helped build the park, makes plans to take him. But, when Clifford reveals himself to be a first-rate brat, his uncle goes bonkers, and a loony inter-generational standoff ensues.