Le souffle du désir(1958)

Daniel Bellanger, a night-club crooner, is a basically straight,honest man. He has just married Christiane, a cashier in a Montmartre hotel and his main objective in life is to live happily with his wife and Pierrot, the son she had of a former union. Unfortunately Daniel accepts the offer of his old friend Freddy to run a gambling den. The place is frequented by a host of dubious guys, among whom a hood named Mario. The latter finds Christiane to his liking and soon shows he is prepared to do anything to take her away from Daniel, including kidnapping little Pierrot.