I think the film is exceptionally moody and sinister—and subtly subversive. Director John Brahm may not have been an auteur, but this German director imported by Fox from England certainly was a master at using light and shadow to induce the creeps. Or was celebrated cinematographer Lucien Ballard the genius? Much has been made of similarities between "The Undying Monster" and "Hound of the Baskervilles" released by Fox three years earlier. But there is more to the similarity than Fox's attempt to cash in on an earlier success. In "Hound of the Baskervilles" Sherlock Holmes debunked the Baskerville curse as a diversion used to cover up a murder attempt. The writers of "The Undying Monster" subverted the audience's belief that there would be a similar natural explanation of an apparently supernatural attack in which a member of the Hammond family is injured. The Hammond curse concerns an ancestor who is supposed to have made a pact with the devil for immortality. The ancient ancestor is still rumored to live in a secret room in the castle's cellar from which he preys on his descendants, thereby prolonging his unnatural life. In this film the murderer is indeed a werewolf.<br/><br/>But this astonishing revelation is muted by a curiously unconvincing final scene in which a forensic pathologist from Scotland Yard, who has witnessed the creature's transformation back into human form, tosses off the unprecedented phenomenon as something perfectly natural. Lycanthropy, says the investigator, is merely a person's delusion that he can change into a wolf. The family doctor admits he has been treating the monster for a genetic brain affliction. But we have seen it was much more that a delusion. We remember what the investigator conveniently forgets, that a sample of wolf's fur from the crime scene miraculously disappeared during chemical analysis. The unwarranted insertion of a "logical" explanation for the curse steers the film away from an uncomfortably audacious premise, and toward the inoffensive conventions of an old dark house mystery.<br/><br/>But the film began with something much more sinister in mind. When Helga, the mistress of the manor, leads investigators to the Hammond family crypt, we see that near Crusader Sir Reginald Hammond's sarcophagus stands a statue of Sir Reginald and a beast that has a dog's, wolf's, or jackal's face and paws, but human arms and unmistakable female breasts. The pathologist dismisses the beast's odd appearance with the facile comment "Man has always bred the dog into fantastic shapes." There are no further references to Sir Reginald, and the final scene feels as if it had been tacked on in post-production, more so because Heather Angel who played Helga, the investigator's love interest, is not in the scene. My guess is that fear of the Hayes office caused Fox not to carry through with the dark suggestion that Sir Reginald's pact unleashed evil upon his descendants. The otherworldy combination of male and female, human and animal characteristics of the wolf in Sir Reginald's statue suggests at the very least he was involved in an unholy union that may have spawned male descendants genetically tainted with diabolical traits. If detected, such a theme would surely have roused the ire of the censors. Fox's timidity may therefore have cost this handsomely mounted film, that sported more elaborate sets and technique than Universal had at its disposal, any chance to join the A list of B films from the 1940s horror cycle.<br/><br/>Nevertheless, it's an entertaining film if you can look past the ending and the comic relief provided by an assistant investigator who comes off as a female version of the bumbling Dr. Watson of the Holmes movies.