A drunken Gypsy couple spending the night in the abandoned Castle Wolfstein accidentally resurrect the werewolf Imre Wolfstein when they remove the silver cross from his corpse. Once alive, he not only kills the Gypsy couple, but also wreaks havoc on a nearby village. The villagers attribute the attack to ordinary wolves, and in response, form a hunting party to kill off the animals. While on the hunt, Count Waldemar Daninsky is attacked by Imre Wolfstein and is afflicted with lycanthropy. After killing innocent victims in the midst of his transformation, he seeks help from specialists, Dr. Janos de Mikhelov and his wife, who turn out to be two vampires, who then prey on both Janice and Rudolph, Waldemar's friends. The vampires revive the first werewolf, Imre, from the dead, and force the two werewolves to battle each other. Waldemar kills Imre Wolfstein with his fangs and then destroys the two vampires, only to be killed in turn by a bullet fired by Janice, the woman who loved him most.
Paul Naschy was the stage name of the late Spanish screenwriter and actor Jacinto Molina. The film's German distributors felt that Molina needed a more Teutonic-sounding pseudonym. “Paul” was an homage to the Pope at the time, Paul VI, and “Naschy” was inspired by a well-known Hungarian Olympic athlete, Imre Nagy. La Marca del Hombre Lobo was the first in a long line of werewolf films that would make Paul Naschy world famous. Naschy got the idea to make a Spanish horror film while he was working on the film Agonizing in Crime in 1967. He broached the idea to the director of that film, Enrique Eguiluz, who initially tried to dissuade him from doing it. Naschy tried to interest Spanish director Amando de Ossorio in the project, who also tried to dissuade him. Finally, Eguiluz changed his mind and helped Naschy find an interested Spanish film producer. In the United States, the film was titled Frankenstein's Bloody Terror, solely to satisfy the American distributor's need for a second "Frankenstein film" to pad out a planned double feature release. To justify this odd choice of title, an animated opening sequence especially created for the film explained that a branch of the Frankenstein family became cursed with lycanthropy and took the name Wolfstein. American producer Sam Sherman needed to fill 400 play dates for his film Dracula vs. Frankenstein which, at that time, was entangled in a legal stand-off with an unscrupulous film lab contracted to produce the release prints. The 400 theaters in question had been promised a Frankenstein double feature, and Sherman was determined to give them one. Both films thus ran together in 1974 in American theaters. La Marca del Hombre Lobo was filmed in Jan Jacobsen’s Hi-Fi Stereo 70 3-D format. When Sherman learned this, he was persuaded by other investors to hire optical effects maestro Linwood Dunn to create single-strip, over-and-under 35mm prints for American release. The final results were reportedly beautiful to look at when projected through high-quality 3-D lenses, but a celebrity-studded Hollywood premiere was completely undone when Sherman’s fellow investors provided shoddy acrylic lenses for the projectors; hence, it was only shown in 70mm 3-D in Germany.
