Calvin Prinz is an only child. The son of a wealthy industrialist, he lives with his two parents in the upscale area of the city. Kevin Bottel, he lives with his mother, his big brother and his little sister. The ends of the month are difficult with only one interim salary. One day, by chance, the two boys meet. They are immediately struck by their physical resemblance. The idea comes to them to exchange their roles for a few days...