Jack Holt

Character: Jack Hart aka Quinn

Constance Cummings

Character: Julie Arnold

Boris Karloff

Character: Jim Henderson

Claude King

Character: Arnold

Bertha Mann

Character: Nurse Edwards

Edward Van Sloan

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

Willard Robertson

Character: Capt. E.J. Hawkes

Thomas E. Jackson

Character: Agent Burke

Martha Mattox

Character: Hotel Ansonia Maid

Jessie Arnold

Character: Eastland Hospital Nurse

Harry Tenbrook

Character: Man in Black / Henchman in Boat