During a brutal winter in the remote Dartmoor village of Sittaford, Major Burnaby, a retired army officer, trudges through snow to Sittaford House, a granite home built by his closest friend, Captain Joseph Trevelyan, a wealthy retired naval officer. Two months earlier, Trevelyan let the house to Mrs. Willett, a widow claiming to be from South Africa, and her daughter Violet, then moved to a small rented house called Hazelmoor in the nearby town of Exhampton, six miles downhill. The Willetts' decision to spend winter on the bleak moor strikes everyone as inexplicable.
The other tea guests include Mr. Rycroft, an elderly gentleman interested in psychic research; Ronald Garfield, a young man visiting his wealthy aunt; and Mr. Duke, a quiet, self-contained man who recently purchased one of Trevelyan's cottages. After tea, Ronnie proposes table-turning, a parlour game in which participants place their hands on a small table and invite spirits to spell out messages. The table initially produces playful responses, but a new force directs a message at Burnaby, slowly spelling "TREVELYAN," then "DEAD," then "MURDER." All deny pushing the table. Mr. Rycroft notes the time: 5:25. Despite protests about the dangerous weather, Burnaby insists on walking to Exhampton to check on his friend.
He arrives at Hazelmoor just before eight o'clock, exhausted. With the help of Constable Graves and Dr. Warren, he finds the study's French window ajar, the room ransacked, and Trevelyan dead from a fractured skull. The weapon is a sand-filled draught excluder, a long fabric tube normally placed against doors to block cold air. Warren estimates death occurred two to three hours earlier; when Burnaby asks if Trevelyan could have died at 5:25, Warren confirms that is precisely the time he would suggest.
Inspector Narracott arrives from Exeter the next morning and concludes the burglary was staged: The window was merely splintered to simulate a break-in. Evidence suggests the murderer entered through the window yet was someone Trevelyan admitted willingly. Evans, Trevelyan's former servant, last saw his master at two o'clock Friday and confirms the Willetts were strangers. At the Three Crowns inn, proprietress Mrs. Belling reveals that a young stranger named James Pearson stayed there Friday night, going out around half past four and returning about 20 past six. When the will is read, the estate, worth roughly 80,000 to 90,000 pounds, is divided among Trevelyan's sister Jennifer Gardner and the three children of his deceased sister: James, Sylvia, and Brian Pearson.
Narracott interviews Jennifer in Exeter, a commanding woman whose husband Robert is bedridden with shell shock, a condition now known as post-traumatic stress disorder. She explains her estrangement: Trevelyan refused her a loan when Robert desperately needed treatment. At Jim Pearson's London lodgings, the haggard young man admits visiting his uncle on Friday but gives a halting account, claiming he left Trevelyan alive at a quarter past five and fled Exhampton the next morning after hearing about the murder. Emily Trefusis, Jim's fiancée, arrives. Sharp and determined, she tells Jim bluntly he lacks the nerve for murder and pledges to clear his name.
Jim is arrested after the inquest. Emily approaches Charles Enderby, a young journalist from the
Daily Wire in Exhampton to present Burnaby with a 5,000-pound prize from a football betting competition. She proposes a partnership: exclusive interviews in exchange for investigative help. She flags the Willetts' mysterious presence and the séance as key puzzles. Emily and Charles drive to Sittaford, where they take rooms at Mrs. Curtis's cottage and learn a convict has escaped from the nearby Princetown prison.
Emily systematically works through the residents. Miss Percehouse, Ronald Garfield's aunt and a bedridden but razor-sharp elderly woman, provides a crucial clue: a luggage label proving the Willetts came from Australia, not South Africa. At Sittaford House, Emily meets the nervous Violet, deliberately leaves her gloves behind, and on returning overhears Mrs. Willett wailing through a closed door: "My God, I can't bear it. Will tonight never come?" (158). Suspecting something significant is planned for that evening, Emily instructs Charles to keep watch on the house overnight.
Solicitor Mr. Dacres reveals that Jim had been secretly borrowing from his insurance firm to speculate in shares, giving him an urgent financial motive the police already know about. That night, Charles stakes out Sittaford House and catches Violet slipping out at midnight to meet a man. After a scuffle, the stranger is revealed as Brian Pearson, Jim's younger brother, supposedly in Australia. Brian refuses to explain his movements. Narracott also discovers that Sylvia's husband, novelist Martin Dering, lied about his whereabouts on Friday, though further investigation proves inconclusive regarding the murder.
Emily receives a letter from Mrs. Belling reporting that a pair of Trevelyan's thick winter boots has gone missing from Hazelmoor. She obtains the key and searches the house. A pile of soot in the bedroom catches her eye. Reaching up the chimney, she pulls out the missing boots, wrapped in newspaper: They are ski boots. In the cupboard of sporting equipment downstairs, she finds two pairs of skis. The boots fit the longer pair, but the toe clips on the shorter pair are adjusted for a much smaller foot, meaning someone else's skis have been hidden among Trevelyan's possessions. The solution crystallizes: Major Burnaby is the murderer.
Emily presents the evidence to Narracott. That afternoon at Sittaford House, Mr. Rycroft persuades the group to repeat the séance. They sit in darkness when a thunderous knock at the front door shatters the silence. Narracott enters and formally charges Major John Burnaby with murder.
Burnaby engineers the original séance to create a compelling reason to rush to Exhampton, establishing his presence at Sittaford at 5:25 as an alibi. He goes home, straps on skis, and skis downhill in roughly 10 minutes. He raps on the study window, is admitted by his unsuspecting friend, and strikes him from behind. He fakes the burglary, hides the skis among Trevelyan's equipment, stuffs the boots up the chimney, then detours to the road and arrives on foot just before eight, appearing exhausted. His motive: Trevelyan composes the winning competition entry but submits it under Burnaby's name, and Burnaby, who has lost heavily on investments, decides to keep the prize money by ensuring Trevelyan can never claim it.
The secondary mysteries resolve as well. Violet confides that her father is the escaped Princetown convict; the Willetts come from Australia and rent Sittaford House to be near the prison and engineer his escape. Brian Pearson, who falls in love with Violet on the voyage, helps plan the escape, explaining his secrecy. Mr. Duke is revealed as a retired Chief Inspector from Scotland Yard whose expertise aided Narracott's investigation. Charles proposes to Emily, but she refuses, declaring she loves Jim. With Jim cleared of the murder charge, Emily departs for London to persuade his firm not to prosecute him for the embezzled funds. Mrs. Curtis compares Emily to a formidable relative who married a handsome but hopeless man and made his fortune through sheer determination, predicting Emily will do exactly the same.