Sally Farnham and her husband Alex inherit an old mansion from Sally's recently deceased grandmother. Shortly after moving in, she discovers a bricked-up fireplace in the basement den. The estate's handyman, Mr. Harris, tells her that Sally's grandmother had him seal it up after her grandfather died and that it is better to leave it the way it is. After he leaves for the day, she uses some of Harris' tools to try to remove the bricks herself. She fails, but is able to pry open a small side door used for removing fireplace ashes. Inside is not a fireplace at all but a large, dark, deep sub-basement. As Sally leaves the den, several whispering voices call her name from behind the fireplace, proclaiming that "She set us free."Sally begins to feel unsettled in the house. One night she is awakened by voices whispering her name, and an ashtray mysteriously falls off her bedside cabinet. Alex dismisses her concerns and believes she is suffering from nervous tension. The next evening, something grabs her dress as she is walking down the stairs and she hears voices whispering "We want you." Freeing herself, she sees something scuttling away behind a curtain, which she believes is a small animal of some kind. Later, she hears the same whispering coming from behind the fireplace in the basement den. Alex remains unconvinced of her story, but makes sure the ash door is bolted securely shut.The following night, Sally throws a dinner party for Alex's colleagues at his law firm. During the party, Sally sees a small, hideous goblin-like creature near her leg under the dinner table. She screams, but nobody believes what she saw and the creature quickly vanishes. Alex grows impatient with her and thinks she is becoming delusional. While Sally is in the shower, three of the goblin creatures turn out the lights so that they can attack her with a razor. As Sally turns the light back on, the creatures shriek and retreat from the brightness into the bathroom cupboards where they disappear. She tells Alex they should sell the house.The following day, Alex goes away on business and Sally arranges to go and stay with her friend Joan. Before she goes, the creatures attempt to trip Sally down a flight of stairs, but they accidentally cause the death of her interior decorator instead. Sally tries to confront the creatures and asks them what they want, and they reply they want her spirit. Whoever frees them (as Sally did by opening the fireplace) must become one of them. Sally's doctor prescribes sedatives and her friend Joan stays with her. Joan begins to believe Sally's story. Alex remains unconvinced. He leaves to meet their handyman regarding the history of the house and the fireplace. Sally tries to stay awake but the creatures put sedatives into her coffee and cut the electricity. They lock Joan outside when she checks the circuit breaker. Sally manages to walk downstairs, but the creatures trip her in the dark. While she is semi-conscious, they drag her into the basement den and into the unsealed fireplace.Sally, now one of the creatures, patiently waits for their next victim to move into the house.