When Dave goes on a business trip to Europe, Simon, Theodore and Alvin are left at home with the accident-prone Miss Miller. Soon Alvin agrees to an offer that will allow the boys to become jet-setters when they participate in an around-the world hot-air balloon race! Their main competitors in the airborne adventure are the Chipettes, but their real opponents turn out to be Klaus and Claudia, two conniving international crooks who use the race to smuggle diamonds.