Boris Karloff

Gen. Nikolas Pherides

Ellen Drew

Thea

Marc Cramer

Oliver Davis

Katherine Emery

Mary St. Aubyn

Helene Thimig

Madame Kyra

Alan Napier

St. Aubyn

Jason Robards Sr.

Albrecht

Ernst Deutsch

Dr. Drossos

Skelton Knaggs

Andrew Robbins (uncredited)

Sherry Hall

Col. Kobestes (uncredited)

Erick Hanson

Officer (uncredited)

Rose Hobart

Mary St. Aubyn (in long shot; uncredited)

Mark Robson