Lewis Barnavelt, after losing his parents, is sent to Michigan to live with his uncle Jonathan. He discovers his uncle is a warlock, and enters a world of magic and sorcery. But this power is not limited to good people: Lewis learns of Isaac Izard, an evil wizard who constructed a magical clock with black magic, as long as it exists it will keep ticking, counting down to doomsday. He died before he could finish the clock, but he hid the clock in his house, where Uncle Jonathan now lives. Now...

A Heffley family road trip to attend Meemaw's 90th birthday party goes hilariously off course thanks to Greg's newest scheme to get to a video gaming convention. This family cross-country adventure turns into an experience the Heffleys will never forget.