The story begins on the first day of the summer vacation, with a family going out for the first few hours in the morning in order to avoid traffic jams. Tom, the father, is behind the wheel, next to his wife, Julia, who is eight months pregnant. Behind them are the nine-year-old daughter and the youngest son of seven. Even further behind is Tom’s father, Ben, who unexpectedly joined them all, much to Julia’s dismay, that he had planned to spend some time with his family, but without his father-in-law. To make matters worse, Ben secretly manages to smuggle a pretty girl aboard, who had been abandoned at a gas station.