Behind the Mask

A federal agent goes undercover to infiltrate a drug smuggling operation led by a mysterious Mr. X, who runs a bogus hospital where victims are killed on the operating table and their coffins filled with narcotics. Jack Holt stars as Jack Hart aka Quinn, while Boris Karloff plays Jim Henderson, a character entangled in Mr. X's sinister scheme. Edward Van Sloan portrays Dr. August Steiner / Dr. Alec Munsell / Mr. X, the mastermind behind the operation.