It's summer vacation, the weather's great, and all the kids are having fun outside. So where's Greg Heffley? Inside his house, playing video games with the shades drawn. Greg, a self-confessed 'indoor person,' is living out his ultimate summer fantasy - no responsibilities and no rules. But Greg's mom has a different vision for an ideal summer, one packed with outdoor activities and 'family togetherness.' Whose vision will win out? Or will a new addition to the Heffley family change everything?