Clark Griswold, an enthusiastic but bumbling family man, is determined to give his family the ultimate vacation experience with a road trip to the famed Walley World amusement park, a clear ode to Disneyland. His eager plans for a cross-country drive from Chicago to California are met with less enthusiasm from his wife, Ellen, and their two teenage children, who would prefer to fly. Undeterred, Clark insists on bonding over the nuances of the American landscape in their Wagon Queen Family Truckster, an exaggeratedly styled station wagon.

As the Griswold family embarks on their journey, a series of comedic misadventures unfolds. The trip takes a comical turn when they get lost in St. Louis, and their car becomes vandalized, leading to an amusing encounter with streetwise locals. The family dynamic is further tested with the unwelcome addition of Ellen's cantankerous Aunt Edna and her dog, who turn the trip into an even more chaotic experience. Mishap follows mishap, including uncomfortable family moments, unexpected animal encounters, and continuous vehicular disasters that all serve to threaten the high spirits of their holiday. Despite the setbacks, Clark's inexorable optimism impels the family to push forward, with each incident adding to the buildup of anticipation for the ultimate destination, the promise of which keeps their spirits precariously afloat amidst the mayhem.