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?