Billy Wilder Director, Writer Tyrone Power Leonard Stephen Vole Actor Marlene Dietrich Christine Helm Vole Actor Charles Laughton Sir Wilfrid Robarts Actor Elsa Lanchester Miss Plimsoll Actor John Williams Mr. Brogan-Moore Actor Henry Daniell Mr. Mayhew Actor Ian Wolfe Mr. Carter Actor Una O'Connor Janet McKenzie Actor Torin Thatcher Mr. Myers Actor Francis Compton Judge Actor Norma Varden Emily French Actor Philip Tonge Inspector Hearne Actor Ruta Lee Diana Actor Ottola Nesmith Miss Johnson (uncredited) Actor Marjorie Eaton Miss O'Brien (uncredited) Actor J. Pat O'Malley Shorts salesman (uncredited) Actor Agatha Christie Writer Lawrence B. Marcus Writer Harry Kurnitz Writer Edward Small Executive Producer Arthur Hornblow Jr. Producer Matty Malneck Original Music Russell Harlan Cinematographer Daniel Mandell Film Editing Alexandre Trauner Art Director Howard Bristol Set Decoration Edith Head Costume Design