Behind the Mask

Jack Holt

as Jack Hart aka Quinn

Constance Cummings

as Julie Arnold

Boris Karloff

as Jim Henderson

Claude King

as Arnold

Bertha Mann

as Nurse Edwards

Edward Van Sloan

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

Willard Robertson

as Capt. E.J. Hawkes

Thomas E. Jackson

as Agent Burke

Martha Mattox

as Hotel Ansonia Maid

Jessie Arnold

as Eastland Hospital Nurse

Harry Tenbrook

as Man in Black / Henchman in Boat