Chapter 1: The Letter
* Dr. Sheppard receives an anonymous letter after returning home from dinner, informing him that his neighbor, Roger Ackroyd, has been murdered.
* The letter mentions that Ackroyd's housekeeper, Ursula Bourne, will die soon.
Chapter 2: The Second Gong
* Sheppard rushes to Ackroyd's house and finds him dead in his study, apparently from a gunshot wound.
* Sheppard calls the police, but before they arrive, he hears a gong sound twice from upstairs.
Chapter 3: The Morning After
* Sheppard learns that Ackroyd's secretary, Geoffrey Raymond, had visited him late the previous night.
* Sheppard also discovers that Ursula Bourne has died from an overdose of digitalis.
Chapter 4: The Missing Letter
* Sheppard realizes that the anonymous letter is missing.
* He suspects that someone in the household may have stolen it.
Chapter 5: The Missing Footprints
* Inspector Poirot arrives and begins investigating.
* He discovers that there are no footprints in the snow leading away from the house, suggesting that the murderer escaped without leaving any traces.
Chapter 6: The Alibi
* Sheppard provides Poirot with an alibi for the time of the murder.
* He claims to have been at home the entire night.
Chapter 7: The Disappearance of Raymond
* Geoffrey Raymond disappears.
* Poirot suspects that Raymond may have been the murderer.
Chapter 8: The Second Letter
* Sheppard receives a second anonymous letter, claiming that the murderer is someone close to him.
Chapter 9: The Puzzle of the Will
* Poirot investigates Ackroyd's will and discovers that it was forged.
* The forged will left the entire estate to Ralph Paton, Ackroyd's adopted son.
Chapter 10: The Secret of the Study
* Poirot uncovers a secret passageway hidden behind a bookcase in Ackroyd's study.
* He also discovers a diary belonging to Ursula Bourne, which reveals that she was blackmailing Ackroyd.
Chapter 11: The Unmasking
* Poirot reveals that the murderer is Caroline Sheppard, Dr. Sheppard's wife.
* Caroline had been having an affair with Ackroyd and had threatened to expose their relationship.
* Ackroyd planned to cut her out of his will, so Caroline murdered him to protect herself.
* She also killed Ursula Bourne to silence her blackmailing.
* Caroline had forged the second anonymous letter to mislead Poirot.
* Poirot had eventually deduced her guilt based on her contradictory statements, the missing footprints, and the discovery of Ursula Bourne's diary.
