On December 15, 1991, Jules and Verne wish their parents a happy anniversary and surprise them with gifts. Jules has discovered, through his own invention (the "JEB Cross-Time Headliner") that December 15, 2091 will be the date of McFly Space Cruises' first voyage to the planet Mars. Using a flux capacitor, a fax machine and "Father's credit card", Jules has also purchased two tickets for Doc and Clara. Moments after their parents have departed, the boys get another headline from the future that says "McFly Solar Sailship Lost In Space!", and set off in the time train to prevent the disaster.