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)