In Paris during 1890, 104-year-old Georges Bonnet (Diffring) is a sculptor who maintains a youthful appearance by regularly murdering women and using their parathyroid glands as an elixir to ward off the signs of age. When Bonnet’s requires a vital surgery to be undertaken he asks his old colleague Prof. Ludwig Weiss (Arnold Marlé) to perform it. He declines and Bonnet then blackmails Pierre Gerard (Christopher Lee) into performing the operation by endangering the life of Janine Dubois (Hazel Court), a young lady both Bonnet and Gerard are romantically interested in.