When Dave embarks on a business trip to Europe, Simon, Theodore and Alvin are left at home in the care of the accident-prone Miss Miller. But soon Alvin and the boys become jet-setters of their own as they participate in an around-the-world hot-air balloon race! Their main competition will be the Chipettes, but their real opponents turn out to be Klaus and Claudia, two international crooks who are using the race as a front for their worldwide diamond smuggling operation.