Ellery Queen, Master Detective

Ralph Bellamy

as Ellery Queen

Margaret Lindsay

as Nikki Porter

Charley Grapewin

as Insp. Queen

James Burke

as Sgt. Velle

Michael Whalen

as Dr. James Rogers

Marsha Hunt

as Barbara Braun

Fred Niblo

as John Braun

Charles Lane

as Dr. Prouty

Ann Shoemaker

as Lydia Braun

Marion Martin

as Cornelia

Douglas Fowley

as Rocky Taylor

Morgan Wallace

as Zachary

Byron Foulger

as Amos

Katherine DeMille

as Valerie Norris

Peter Bronte

as Doctor's Assistant (uncredited)

Jack Cheatham

as Desk Sergeant (uncredited)

Arthur Millett

as Elevator Guard (uncredited)

Frank O'Connor

as Ambulance Driver (uncredited)

Lee Phelps

as Flynn (uncredited)

Jack Rice

as Rogers' Assistant (uncredited)

Alan Ladd

as Elevator Passenger (uncredited) (unconfirmed)