Mexican director Fernando Mendez' 1958 horror masterpiece "The Black Pit of Dr. M" originally appeared under the title "Misterios de Ultratumba" ("Mysteries of the Afterlife"), certainly a more appropriate appellation. In this film, you see, Dr. Masali, head of a rural insane asylum, coerces a dying associate, Dr. Aldama, to show him the secrets of the realm of the dead, and then return him to the land of the living. But poor Dr. Masali should have known that when you make a deal with the soon-to-be-dead, things don't always turn out quite as expected! And they don't, in this very cleverly plotted story that conflates a predestined love affair, an insane gypsy woman, a cursed dagger, disfigurement by acid, transmigration and so much more. Rafael Bertrand is truly excellent as the obsessed Dr. Masali, and special praise must also be heaped on cinematographer Victor Herrera for his work on "Dr. M." His B&W nighttime photography (most of the film does transpire at night) is a thing of real beauty, replete with moving shadows and dense, swirling mists; his work on another of Mendez' horror films from 1958, "The Living Coffin," seems far more pedestrian, in prosaic color. "Dr. M" is the kind of film that serves up a startling plot twist every few minutes or so. I would hate to spoil things for any potential viewer by saying too much, but thus feel that this minireview is not doing this tremendous picture justice. So please just trust me on this one--this film should be required viewing for all horror fans. The fine folks at Casa Negra should be thanked for rescuing this little gem from obscurity, and presenting it via a great-looking, excellently subtitled DVD, and with many fine extras, too. Again, gracias, Casa Negra.