Ellery Queen, Master Detective

Ralph Bellamy

— Ellery Queen

Margaret Lindsay

— Nikki Porter

Charley Grapewin

— Insp. Queen

James Burke

— Sgt. Velle

Michael Whalen

— Dr. James Rogers

Marsha Hunt

— Barbara Braun

Fred Niblo

— John Braun

Charles Lane

— Dr. Prouty

Ann Shoemaker

— Lydia Braun

Marion Martin

— Cornelia

Douglas Fowley

— Rocky Taylor

Morgan Wallace

— Zachary

Byron Foulger

— Amos

Katherine DeMille

— Valerie Norris

Peter Bronte

— Doctor's Assistant (uncredited)

Jack Cheatham

— Desk Sergeant (uncredited)

Arthur Millett

— Elevator Guard (uncredited)

Frank O'Connor

— Ambulance Driver (uncredited)

Lee Phelps

— Flynn (uncredited)

Jack Rice

— Rogers' Assistant (uncredited)

Alan Ladd

— Elevator Passenger (uncredited) (unconfirmed)