Young Greg Heffley is looking forward to a long summer of just hanging out, but his mother throws a monkey wrench into his plans when she forces the entire family to take a road trip for a relative's birthday celebration. His eyes soon light up after he realizes that the excursion is his ticket to a gaming convention to meet YouTube sensation Mac Digby. Greg's imagination then kicks into overdrive as he sneakily hatches a scheme to attend the expo and gain some much-deserved fame.