David Norliss, a writer working on a book debunking spiritualists and fakers, vanishes from his home in
San Francisco, California, leaving behind a series of audio tapes explaining his absence and recent investigations. The narrative unfolds as his publisher listens to the tapes. Norliss had recently investigated an incident reported by Ellen Sterns Cort, a widow who claims that she was attacked by her recently deceased artist husband, James, one night on their estate near
Monterey. James, who had been suffering from a crippling disease, became involved in the occult after meeting a mysterious woman, Mademoiselle Jeckiel, who attended one of his exhibitions. Ellen says James was buried with a mysterious
scarab ring that Jeckiel gave him. That evening in
Carmel, a young motorist is attacked in her car, causing her to crash and die. When she is found her skin is a dark grey, and a coroner later confirms her body was drained of blood. Norliss, not knowing about this, travels to Carmel to meet Sheriff Tom Hartley to discuss Ellen's claims. Later, Norliss and Ellen visit James' crypt on the estate and find the ring on his hand. Norliss goes to San Francisco to meet Charles Langdon, a gallery owner who had called Ellen inquiring about purchasing James's ring. Langdon learns that the ring was buried with James and tries to steal it, but the coffin is empty. As he leaves the crypt he is attacked by the ghoul James. Norliss meets Mademoiselle Jeckiel, who warns him to stay away from the Cort estate. That night, Norliss and Ellen search James' art studio, where they find a large sculpture Ellen says was not there days before. The ghoul James attacks them. Norliss shoots him several times, but James chases them out of the studio. James rips off the door of their car, but they manage to drive away. Sheriff Hartley joins Norliss and Ellen and they find James' crypt empty. Ellen's sister, Marsha, arrives at the Cort estate hoping to spend the night. When she finds nobody home, she instead lodges at a nearby motel. James breaks into the room and carries her into the nearby woods. Norliss' research discovers a series of tunnels had been built on the Cort estate during its construction in the 1920s. Lab results on clay from the large sculpture show it includes human blood. A frightened Jeckiel arrives. She tells Ellen that James has made a pact with the Egyptian deity Sargoth whereby he would create a sculpture through which Sargoth could enter the world. Jeckiel says that to stop James, his scarab ring must be removed. Ellen and Jeckiel search the tunnels for James and find him resting inside a pine box coffin. Jeckiel attempts to remove the ring but James awakens and grabs her. Fleeing through the tunnels, Ellen stumbles upon Langdon's and Marsha's corpses. Norliss finds Ellen in the tunnels and they emerge in James' art studio. Norliss and Ellen hide and watch as James finishes the ritual that summons Sargoth and brings the statue to life. Norliss is able to destroy them by burning the studio to the ground in a manner that Mademoiselle Jeckiel had specified. The publisher finishes listening to the tape, and wonders if Norliss's disappearance is related to the incident described on it. He begins to play another tape. ==Cast==