Robert Curtis, a Scotland Yard police inspector, and Christy, a female detective fascinated with the occult, have their work cut out for them when they investigate the savage attack on Oliver Hammond, a wealthy aristocrat, and Kate, a young nurse. The superstitious butler, Walton, believes that a creature who has menaced the Hammond family for years is on the prowl again. Oliver's sister, Helga, is more skeptical, and so is Dr. Colbert, the family friend and physician. The detectives' search through the Hammonds' gloomy old mansion yields secrets that several persons are desperate to keep hidden.
