A middle-aged playboy becomes fascinated by the daughter of a private detective who has been hired to entrap him with a client's wife.

Gary Cooper
as Frank Flannagan

Audrey Hepburn
as Ariane Chavasse / Thin Girl

Maurice Chevalier
as Claude Chavasse

John McGiver
as Monsieur X

Van Doude
as Michel

Lise Bourdin
as Madame X

Olga Valéry
as Hotel Guest with Dog

Paul Bonifas
as Police Chief (uncredited)

Audrey Long
as Brunette (uncredited)

Charles Lemontier
as General (uncredited)