The Haunting of Hill House is a supernatural novel about four people who come together to spend a week in a haunted house. Eleanor, a timid woman who has spent most of her life caring for her unpleasant mother, feels free for the first time in years, and is both scared and enamored of the house. The novel explores the themes of nature, sexuality, and sanity, and uses an unreliable narrator to play with the reader's perception of reality.
Hill House is an eighty-year-old mansion in a location that is never specified, built by long-deceased Hugh Crain. The story concerns four main characters: Dr. John Montague, an investigator of the supernatural; Eleanor Vance, a shy young woman who resents having lived as a recluse caring for her demanding invalid mother; Theodora, a flamboyant, bohemian, possibly lesbian artist; and Luke Sanderson, the young heir to Hill House, who is host to the others.
Dr. Montague hopes to find scientific evidence of the existence of the supernatural. He rents Hill House for a summer and invites as his guests several people whom he has chosen because of their past experience with paranormal events. Of these, only Eleanor and Theodora accept. Eleanor travels to the house, where she and Theodora will live in isolation with Montague and Luke.
Hill House has two caretakers, Mr. and Mrs. Dudley, who refuse to stay near the house at night. The blunt and single-minded Mrs. Dudley is a source of some comic relief. The four overnight visitors begin to form friendships as Dr. Montague explains the building’s history, which encompasses suicide and other violent deaths.
All four of the inhabitants begin to experience strange events while in the house, including unseen noises and ghosts roaming the halls at night, strange writing on the walls and other unexplained events. Eleanor tends to experience phenomena to which the others are oblivious. At the same time, Eleanor may be losing touch with reality, and the narrative implies that at least some of what Eleanor witnesses may be products of her imagination. Another implied possibility is that Eleanor possesses a subconscious telekinetic ability that is itself the cause of many of the disturbances experienced by her and other members of the investigative team (which might indicate there is no ghost in the house at all). This possibility is suggested especially by references early in the novel to Eleanor's childhood memories about episodes of a poltergeist-like entity that seemed to involve mainly her.
Later in the novel, the bossy and arrogant Mrs. Montague and her companion Arthur Parker, the headmaster of a boys’ school, arrive to spend a weekend at Hill House and to help investigate it. They, too, are interested in the supernatural, including séances and spirit writing. Ironically, and unlike the other four characters, they do not experience anything supernatural, although some of Mrs. Montague’s alleged spirit writings seem to communicate with Eleanor. Mrs. Montague's haughtiness and self-importance provide another source of comic relief.
Much of the supernatural phenomena that occur are described only vaguely, or else are partly hidden from the characters themselves. Eleanor and Theodora are in a bedroom with an unseen force trying the door, and Eleanor believes after the fact that the hand she was holding in the darkness was not Theodora’s. In one episode, as Theodora and Eleanor walk outside Hill House at night, they see a ghostly family picnic that seems to be taking place in daylight. Theodora screams in fear for Eleanor to run, warning her not to look back, though the book never explains what Theodora sees.
By this point in the book, it is becoming clear to the characters that the house is beginning to possess Eleanor. Fearing for her safety, Dr. Montague and Luke declare that she must leave. Eleanor, however, regards the house as her home and resists. Dr Montague and Luke force her into her car; she bids them farewell and drives off, but before leaving the property grounds she propels the car into a large oak tree, and it is assumed that she is killed. In the short, final paragraph that follows, the reader is left uncertain whether Eleanor was simply an emotionally disturbed woman who committed suicide, or whether her death at Hill House has a supernatural significance.