Three quarters of what you hear here are the ravings of imbeciles. Anaemic Dr Callistratus (Donald Wolfit) is bringing criminally insane prisoners at his remote castle asylum into the lab to take their blood because mistaken villagers put him to death after mistaking him for a vampire. Resuscitated through a heart transplant, he needs a regular supply of blood. Poor Dr John Pierre (Vincent Ball) fetches up there instead of a penal colony for medical malpractice following a blood transfusion that goes wrong . We are in deepest Transylvania in the 1870s and when John’s fiancee Madeleine (Barbara Shelley) follows her beloved you can imagine the consequences … You might find it hard to stifle a giggle when you see Victor Maddern turn up as Carl the one-eyed hunch-backed enforcer in the imaginatively named village of Carlstadt but otherwise this takes itself very seriously indeed, which is how it should be. The topic of medical experiments made a lot of people squirm in the wake of finding out what the Nazis had been up to in WW2 so this had a weird kind of topicality in genre form: exchanging one person’s entire bloodstream for another’s? Why not? Theatrical actor-manager legend Wolfit eats up the screen as the baddie and Ball and Shelley are a very attractive couple battling the madmen and the dogs. Woof! Written by Hammer stalwart Jimmy Sangster who had just written that studio’s first two big hits (also in colour) and directed by Henry Cass.