The novel begins with the journey of a country doctor to an old, eighteenth century mansion with its better days behind it. Dr Faraday has been called to the house to treat a young maid who works there. She hates her job and she hates the spooky, drafty house, with its creaks and the oppressive feeling of loneliness that it seems to exude. However, one thing she does like about the job is the daughter of the family she works for. Caroline Ayres is unmarried and therefore still lives in the family home, and the two young women strike up an easy, if unlikely, friendship. She also becomes friendly with Caroline's brother Roderick Ayres. He has recently returned from the Second World War, where he saw combat as a pilot. Dr Farady has been treating Roderick for a while as well. Roderick's injuries are not heeling as quickly as they should, and the doctor pays so many visits to the Ayres house that he develops a friendship with the entire family. The more time he spends with them the more he realizes that they are financially crippled, and the house is too big for them.
The family are desperate to raise the spirits of all in the house. They decide to have a party, ostensibly to enjoy the company of friends, but in reality they are trying to matchmake Caroline with a young man they feel will make a suitable husband for her. One young couple in attendance has brought their infant son with them, and inexplicably the child is attacked by Caroline's dog, who has never shown any type of aggression before and has been a calm, sweet and loyal dog. The mood sinks further because of Roderick's mood, which Dr Faraday attributes to the stress that he is under, and partially to the "shell shock" - what we would now call post traumatic stress disorder - that he has been suffering from since returning from the war.
A few days after the party, Roderick tells Dr Faraday that the night of the party he saw an unexplained presence in his room. It was malevolent and trying to harm him. He knew instinctively that he needed to occupy the presence, and prevent it from discovering Caroline, or his mother. Strange marks start to appear on his walls. When Caroline finds his room on fire in th middle of the night, and finds him passed out, drunk, he is committed to a mental asylum.
Dr Faraday and Caroline walk a fine line between friendship and romance. Meanwhile, things in the house take stranger and stranger turns; unexplained childish handwriting appears on the walls. The bells that normally summon the maids sound without anyone actually ringing them. The telephone rings but when it is answered, there is only silence on the other end of the line. Mrs Ayres becomes locked in the nursery where her first-born daughter Susan died from diphtheria. Mrs Ayres has a panic attack and sees strange shapes and figures that she cannot discern or decipher. She flails at the windows to escape, hitting them so hard that she cuts herself. Caroline and the maids manage to set her free and when she calms down, she is actually comforted by the feeling that Susan never left and is around her all the time. Unfortunately she then attributes the unexplained noises and writing to Susan and interprets this message as Susan being impatient to see her and she hangs herself.
On the day of her funeral, Dr Faraday and Caroline decide to get married. They set a date for six weeks hence. However, Caroline seems depressed. She is not the excited bride one might expect and is listless and disinterested in life in general. She calls off the wedding and puts Hundreds Hall on the market. Dr Faraday is blindsided by this and tries to talk her into re-scheduling the wedding but her mind is made up. On the night that should have been their wedding night, he is delayed on a house call. When he returns home he discovers that Caroline has killed herself by jumping from the second floor onto the marble floor below. At the inquest, the maid informs the coroner that she heard Caroline go upstairs because she had been awoken by a noise and wanted to investigate what had made it. The maid then heard her exclaim, "You!" before falling. Faraday continues to be tormented by what has happened. For the next three years, he revisits the mansion, desperately trying to find out what it was that Caroline had heard. He never does.
