Boris Karloff

Dr. Janos Rukh

Bela Lugosi

Dr. Felix Benet

Frank Lawton

Ronald Drake

Frances Drake

Diana Rukh

Violet Kemble Cooper

Mother Rukh

Beulah Bondi

Lady Arabella Stevens

Walter Kingsford

Sir Francis Stevens

Paul Weigel

Monsieur Noyer

Frank Reicher

Professor Meiklejohn

Georges Renavent

Chief of the Surete

May Beatty

Mme. LeGrand (uncredited)

Paul McAllister

Papa LaCosta (uncredited)

Nydia Westman

Briggs (uncredited)

Ynez Seabury

Celeste (uncredited)

Robert Graves

Gendarme (uncredited)

Lambert Hillyer