The story is set in Stockholm where 11-year-old Reine is on the verge of puberty and afraid of sexual maturity. He lives in a suburb with his single mother who sends him to one of the traditional Swedish summer camps which were common at the time of the setting and were managed by the cities for children in need of visiting the countryside. The title of the film refers to an island that is home to many such camps. His mother then vacations on her own, but in fact Reine never goes to the camp. Instead he spends the summer exploring the city of Stockholm on his own, where he meets several strange adults.