Rod Taylor as Peter McDermott

Catherine Spaak as Jeanne Rochefort

Karl Malden as Keycase Milne

Melvyn Douglas as Warren Trent

Merle Oberon as The Duchess Caroline

Richard Conte as Detective Dupere

Michael Rennie as Geoffrey - Duke of Lanbourne

Kevin McCarthy as Curtis O'Keefe

Carmen McRae as Christine

Alfred Ryder as Capt. Yolles

Roy Roberts as Bailey

Al Checco as Herbie Chandler

Sheila Bromley as Mrs. Grandin

Harry Hickox as Sam

William Lanteau as Mason

Ken Lynch as Joe Laswell

Clinton Sundberg as Lawrence Morgan

Tol Avery as Kilbrick

Davis Roberts as Dr. Elmo Adams

George Boyce as Bellhop

Charles Alvin Bell as Vickery

Robert Goodwin as Henry

Jack Donner as Elliott (uncredited)

Lester Dorr as Cy - Elevator Operator (uncredited)

Vince Howard as Tousaint (uncredited)

Dorothy Konrad as Housekeeper (uncredited)

Judy Norton as Daughter (uncredited)

John Sebastian as Giotti (uncredited)

William Swan as Young Desk Clerk (uncredited)

Arthur Tovey as Hotel Patron (uncredited)

Ivan Bonar as Silverstein (uncredited)