The Purple Baron, a pilot who flies a biplane, has frozen all of the people in Mumbly and Shnooker's city by using his immobiliser beam! Mumbly was not affected by the beam, and he notices that no one is moving when driving to the police headquarters. Shnooker is frozen, but he left a message for Mumbly on a tape recorder. Shnooker tells Mumbly that Purple Baron shoplifts and robs people of their money while they are immobilized, and the dog detective has to stop him.