When his cousin Sam visits London from America, Matthew's life changes drastically: Sam is rude, smells bad, has long hair, and gets Matthew and his friends into quite a bit of trouble. Before they can welcome him into their group, Sam must pass a test: he has to spend a week, exactly five school days, as a girl. "Sam as in Samantha," Jake said. "All you have to do is be a girl for five days at school. If you agree to do that, you're in. You're one of us." What starts as a joke quickly turns serious when Sam's father comes to London to bring his son back home.