Marianne (Yvonne Monlaur), a beautiful young girl, is stranded en route to a teaching assignment in Eastern Europe. She is persuaded to spend the night at the nearly deserted castle of the mysterious Baroness Meinster (Martita Hunt). In the castle, Marianne accidentally discovers a man chained to the wall in his room. The Baroness explains only that he is her "sick and feeble-minded" son. Unable to get any further information from her or the maid, Marianne steals a key and sets him free. But once unbound, the man–Baron Meinster (David Peel)–fiendishly recruits the undead for his evil purposes while Marianne and Dr. Van Helsing (Peter Cushing) try to stop him in this classic Hammer Film.