Spots 
Hastings arrives at Styles Court during World War I to recover on sick leave. He finds his old acquaintance John Cavendish living with his wealthy stepmother, Mrs. Inglethorp, who has recently married a much younger, suspicious man named Alfred Inglethorp. The household is filled with resentment over money and influence, while residents like Evelyn Howard openly distrust the new husband.
CHAPTER I. I GO TO STYLES
Life at the estate proceeds through village entertainments, hospital visits, and domestic errands. Hastings encounters Hercule Poirot, a renowned Belgian detective staying as a refugee in the local village. Mrs. Inglethorp appears agitated by mysterious letters and household interactions late in the day, signaling hidden friction just before retiring for the night.
CHAPTER II. THE 16TH AND 17TH OF JULY
Mrs. Inglethorp suffers violent convulsions behind a locked door in the early morning hours and dies despite medical efforts. Her missing husband and strange final words trigger immediate suspicions of foul play. The circumstances of her locked room and unusual physical symptoms point toward rapid poisoning rather than natural heart failure.
CHAPTER III. THE NIGHT OF THE TRAGEDY
Poirot joins Hastings to inspect the crime scene at Styles Court, emphasizing that no physical detail is too small to examine. He scrutinizes locked doors, coffee cups, and scraps of burned paper, looking for inconsistencies in time and behavior. While others leap to hasty conclusions about obvious suspects, Poirot systematically gathers facts.
CHAPTER IV. POIROT INVESTIGATES
Poirot analyzes coffee grounds and questions household members about their daily routines, uncovering subtle discrepancies. A lawyer arrives to discuss Mrs. Inglethorp's affairs, confirming that her sudden death interrupted major decisions about her estate. Poirot focuses on minor details, such as unused sugar, that reveal deeper truths about what occurred on the fatal night.
CHAPTER V. “IT ISN’T STRYCHNINE, IS IT?”
Toxicologists confirm at the inquest that Mrs. Inglethorp died from a fatal dose of strychnine. Theories about accidental self-poisoning through regular tonics are ruled out due to the required dosage. Witnesses reveal the timeline of events, including an intense argument the afternoon prior, narrowing suspicion onto those with immediate access to her food and drink.
CHAPTER VI. THE INQUEST
Detectives prepare to arrest Alfred Inglethorp based on overwhelming circumstantial evidence, including a local poison purchase under his name. Poirot intervenes with evidence that disproves the charge, arguing that true guilt is rarely so neatly presented. He demonstrates that obvious clues were deliberately staged to frame the most convenient suspect.
CHAPTER VII. POIROT PAYS HIS DEBTS
With Inglethorp's alibi established, suspicion spreads among the remaining family members and guests. Poirot quietly observes movements and tests physical acoustics around the estate to verify claims made by witnesses. Meanwhile, unexpected connections between household members and outside figures reveal layers of hidden motives.
CHAPTER VIII. FRESH SUSPICIONS
Subtly placed messages test suspicions around Lawrence and other residents, revealing how fear distorts their responses. Tensions peak during private arguments between John and Mary Cavendish regarding outside friendships and hidden loyalties. Poirot uses these emotional strains to discern who is protecting a loved one and who is concealing a crime.
CHAPTER IX. DR. BAUERSTEIN
The arrest of Dr. Bauerstein for wartime espionage clears up his suspicious nocturnal movements without solving the murder. Meanwhile, physical clues like shipping labels and altered wire mechanisms help Poirot reconstruct how entry and timing were manipulated. Each resolved side-issue sharpens the focus back onto the estate's core inheritance conflict.
CHAPTER X. THE ARREST
John Cavendish stands trial for murder after strychnine is discovered in his room and evidence of financial desperation comes to light. The prosecution constructs a compelling story based on his quarrel with his stepmother and alleged destruction of her will. Poirot remains quiet, knowing the prosecution's narrative hinges on a fundamental misinterpretation of the evidence.
CHAPTER XI. THE CASE FOR THE PROSECUTION
Poirot gathers the household to explain how Mrs. Inglethorp herself burned her updated will after discovering a betrayal within her own home. He demonstrates how entry into her room was gained and how key witnesses misrepresented their actions to protect personal secrets rather than cover a murder. The true missing link completes the chain of evidence.
CHAPTER XII. THE LAST LINK
Poirot details how Evelyn Howard and Alfred Inglethorp conspired together from the start, using a chemical reaction in a routine bromide tonic to delay the poison's effect. By intentionally baiting an early arrest that would fail, they sought absolute immunity under the law. Their calculated scheme collapsed only because Poirot recognized how manufactured clues were used to manipulate the investigation.
CHAPTER XIII. POIROT EXPLAINS
Master the art of reading past staged evidence to uncover hidden motives and complex deception.