Montreal, 1940. The Second World War is raging in Europe. Pierre Sauvageau, 22, would like to enlist, but he has to take care of his twin sister, crippled from birth. This proximity awakens the sensuality of Berthe who tries to seduce her brother. Pierre rejects her advances, but when he falls in love with Marguerite, his best friends girlfriend, he is haunted by the fantasy of his sister.