Kurt Ingston presides over a secluded estate in a small town that borders a murky swamp, a place where rumors and unexplained murders swirl around his home. Wheelchair-bound yet highly respected, he has invited the three doctors who once tried to cure his paralysis to return to his house. In the dim corridors and dimmer rooms of the Ingston residence, a tense balance holds: the grim-humored butler Bela Lugosi as Rolf, the lecherous chauffeur Leif Erickson as Laurie, the mannish housekeeper Doris Lloyd as Miss Judd, the Eastern mystic Nils Asther as Agar Singh, and Ingston’s allegedly mentally ill sister, Margaret, portrayed by Fay Helm. Outside, at the gate, a shriveled old hunchback named Torque keeps watch, a haunting figure in the background.
The arrival of a new presence shifts the balance: Dr. Lynn Harper, introduced by Margaret in a bid to prove she is not insane and win her freedom from the household control, comes to the mansion with a neighbor who becomes involved in the mystery. The neighbor is the mystery-writer Dick Baldwin, Don Porter stepping into the scene after rescuing Harper when her car falters in the swamp. The tension between the doctors and the household is palpable from the start, as the three doctors—Lionel Atwill as Dr. King, Frank Reicher as Dr. Timmons, and Francis Pierlot as Dr. Phipps—sit down to dinner and watch Ingston’s suspicions grow that they are somehow responsible for his condition.
During the meal an astonishing demonstration follows: Agar Singh materializes the bones of a Sicilian skeleton, a chilling display that unsettles Harper and foreshadows the peril to come. Harper is warned away from Margaret, and the group prepares for the night as the doctors—now clearly perceived as threats by Ingston—settle in for rest. One by one, the doctors are attacked and killed as they prepare for bed, their fates sealed in the oppressive atmosphere of the house.
Dick and the steady Captain Beggs, Robert Homans, press the investigation, haunted by the possibility that Ingston himself has a hand in the murders. The truth, however, emerges with a shocking revelation: Ingston is not paralyzed at all but a triple amputee, enabling him to manipulate his own body in ways that mimic the affliction he had when the doctors first tried to cure him. Suspicion falls on Laurie, who was last seen driving an ex-employee of the household back to town, but the chauffeur also meets a violent end, extending the circle of death.
As the net tightens, Dick confronts the killer outside the estate as he threatens Harper. The killer is revealed to be Ingston himself: through the tutelage of Agar Singh, he has learned how to conjure and momentarily materialize arms, legs, hands, and feet to carry out his crimes. In the final struggle, Margaret, driven to desperation, sets the house on fire, taking Miss Judd with her in a symbolic end to the household’s dark conspiracy. The flames consume the mansion, and as the inferno rages, Agar Singh intervenes, shooting Ingston and saving Dick and Harper from the murderous plan that Hatched within the swamp-dark walls.
