Rusty Griswold, a pilot for a low-budget airline, decides to take his family on a cross-country road trip to Walley World, an amusement park from his childhood, in hopes of revitalizing their bond and creating lasting memories. He surprises his wife, Debbie, and their two sons, James and Kevin, with the vacation plan, renting a dubious rental car for the journey. Along the way, they face a series of misadventures and mishaps, which include interactions with quirky relatives and bizarre locals, ultimately testing the strength of their relationships and their patience.

As Rusty's well-intentioned plans go increasingly awry, they encounter a variety of challenges that range from mechanical issues with their peculiar Albanian rental car to unpleasant situations at motels and tourist traps. Throughout these ordeals, the family is forced to confront their differences and personal frustrations. Deb contemplates the state of their marriage, while their sons struggle to appreciate one another. Despite the chaos and conflict, Rusty's unwavering determination to forge happy memories drives them forward, setting the stage for a potential change in their journey's course as they approach their final destination.