The tale starts with two unhappy children. Julien is endlessly energetic but unable to bear the impending heartbreak of his beloved mother's death. Sophie is wildly imaginative yet in search of someone to accept and love her. Every time they exchange a symbolic tin box (a gift to Julien from his mother), the one who takes the toy also has to take a dare. Each prank they force one another to play becomes a little bigger, a little more irreverent, a little riskier than the last.