Dennis and his faithful hound Gnasher are out to make every day as much fun as possible, but their adventures often lead them into trouble. After one of Dennis's pranks lands Walter in detention, Walter's parents invite Dennis and his parents over for dinner to trick the menace into confessing. When things don't go according to plan, a challenge is issued by Dennis's Dad: Dennis will behave for a whole evening, if Walter's Dad will dare to misbehave! Will the promise of an afternoon at the Beanotown fair be enough to tempt Dennis to behave himself, or will the urge to menace become too great?!