Sherlock Holmes investigates strange and tragic happenings in a village that appear linked to a man who seems to be like a vampire.
Colonel James Damery calls on Holmes when the rich and beautiful Miss Violet Merville announces her engagement to Baron Gruner, a dangerous Austrian. Gruner has persuaded Violet that he is not a killer, and Holmes has to establish the truth and foil the powerful baron.
The daughter of scientist Professor Presbury sees her father's face at her second-storey window; Holmes connects this with recent zoo thefts.
Holmes investigates a killing which has all the hallmarks of the worst kind of Ruritanian vampire. He is sceptical (to say the least) about the possibility that the undead are up to their mischief just a short train journey from his rooms in Baker Street. If a local resident really found his South American wife sucking blood from their young son, what might it signify?