In this French comedy, a clever fellow proves himself smarter than the gangsters who would exploit him. The trouble begins in Paris when the vacationing hero accidentally gets into an auto accident with a smuggler. The crook is most apologetic for the mishap and kindly offers to let him drive his Cadillac to Bordeaux and continue with his holiday. The poor traveler doesn't know that the vehicle is a black market on wheels carrying everything from jewels to heroine. He is pursued by the smuggler and by a rival gang. He is so busy enjoying himself that he doesn't bother to look back at the gun battles raging behind him. He ends up picking up two hitchhiking women and continuing his leisurely journey. When he finally realizes that they are using him, he drives the crooks right to the police station. Later he discovers that the steering wheel of the car contains the largest diamond in the world.