An architect and his wife are staying in an empty castle in California. They are joined by an unhappily married lawyer and his wife. Things start getting strange when they spot a half man/half beast prowling around the house and keep seeing a headless woman wandering the grounds.

Scott Campbell, an architect, and his wife Nancy, a decorator, visit an old mansion to survey it for his lawyer friend, Joseph Schiller. The mansion, built by an eccentric millionairess who is now confined in an asylum, was last occupied by a recluse, retired circus side show operator Captain Arbuckle. After a series of strange events, Schiller's wife, Loy, disappears. Eventually, the body of the circus showman is discovered not far from Loy's apparently decapitated body. Investigation reveals a troupe of circus freaks secretly living in the castle, having stayed on after their boss's natural death. The freaks used carnival tricks to fake Loy's death so as to frighten the strangers from the castle. Loy is returned to her husband, and the freaks return to the outside world.