A Heffley family road trip takes an unexpected turn when Greg’s latest plan to attend a video gaming convention clashes with the family’s original destination—Meemaw's 90th birthday party. Greg’s well-meaning but often misguided schemes cause a series of hilarious mishaps, detours, and family chaos, all while trying to get to the convention without disappointing his family. Along the way, Greg learns a thing or two about family, priorities, and the sometimes unplanned joy of a road trip gone awry.