It's summer, the holidays, the weather is good, all the young people are taking the opportunity to go out. But where is Greg Heffley hiding? He is at home, watching video games, behind his closed shutters. Greg himself admits that he loves to stay quiet at home! And this summer, he decided to spend it in total fantasy, without constraints and without rules. Unfortunately, Greg's mother doesn't have at all the same vision as him: an ideal summer is one where we indulge in lots of activities outside and as a family! Which of the two will win? Will a new arrival in the family turn everything upside down?