Behind the Mask

John Francis Dillon

Director

Jack Holt

Jack Hart aka Quinn

Constance Cummings

Julie Arnold

Boris Karloff

Jim Henderson

Claude King

Arnold

Bertha Mann

Nurse Edwards

Edward Van Sloan

Dr. August Steiner / Dr. Alec Munsell / Mr. X

Willard Robertson

Capt. E.J. Hawkes

Thomas E. Jackson

Agent Burke

Martha Mattox

Hotel Ansonia Maid

Jessie Arnold

Eastland Hospital Nurse

Harry Tenbrook

Man in Black / Henchman in Boat