[13] Dr James Sheppard, the story's narrator, lives with his unmarried sister, Caroline, in the English country village of King’s Abbot.

Telling the story in his own words, Dr Sheppard recounts being called to certify the death of a wealthy widow, Mrs Ferrars, who has committed suicide a year after her abusive husband's demise.

Roger Ackroyd, wealthy widower and owner of Fernly Park, tells Dr Sheppard that he needs to talk to him urgently and invites him to dinner that evening.

In his study after dinner, Ackroyd tells Dr Sheppard that he had been engaged to Mrs Ferrars for several months, and that she had admitted the day before that she had indeed poisoned her husband.

Unable to get a response at the study door, Sheppard and Parker break it down and find Ackroyd dead in his chair, killed with his own dagger.

The window of opportunity for the murderer after Dr Sheppard's departure appears to have been quite short since Raymond and Blunt later heard Ackroyd talking in his study, and Flora says she saw him just before going up to bed.

Flora is forced to admit she never in fact saw her uncle after dinner, leaving Raymond and Blunt as the last people to hear Ackroyd alive.

He left publicly through the front door, then put Ralph's shoes on, ran round to the study window and climbed back in.

Locking the door from the inside, he set a desk dictaphone going, playing a recording of Ackroyd's voice, and pulled out a chair to hide it from the sightline of anyone standing in the doorway.

While Sheppard had the study to himself for a few minutes after the crime was discovered, he slipped the dictaphone into his medical bag, and put the chair back in place.

Poirot tells Dr Sheppard the matter will be reported to the police in the morning and suggests he spare his sister Caroline by taking his own life.

It includes an unexpected plot twist towards the end, when Dr Sheppard reveals he has throughout been an unreliable narrator, using literary techniques to conceal his guilt without writing anything untrue (e.g., "I did what little had to be done" at the point where he slipped the dictaphone into his bag and moved the chair).

The review in the Times Literary Supplement began, "This is a well-written detective story of which the only criticism might perhaps be that there are too many curious incidents not really connected with the crime which have to be elucidated before the true criminal can be discovered".

In the present case his identity is made all the more baffling through the author's technical cleverness in selecting the part he is to play in the story; and yet her non-committal characterization of him makes it a perfectly fair procedure.

[11]The Observer had high praise for the novel, especially the character Caroline: No one is more adroit than Miss Christie in the manipulation of false clues and irrelevances and red herrings; and The Murder of Roger Ackroyd makes breathless reading from first to the unexpected last.

It is unfortunate that in two important points – the nature of the solution and the use of the telephone – Miss Christie has been anticipated by another recent novel: the truth is that this particular field is getting so well ploughed that it is hard to find a virgin patch anywhere.

But Miss Christie's story is distinguished from most of its class by its coherence, its reasonableness, and the fact that the characters live and move and have their being: the gossip-loving Caroline would be an acquisition to any novel.

[4]The Scotsman found the plot to be clever and original: When in the last dozen pages of Miss Christie's detective novel, the answer comes to the question, "Who killed Roger Ackroyd?"

She also acknowledged taking inspiration from the infamous case of the unsolved death of Charles Bravo, who she thought had been murdered by Dr James Manby Gully.

[25]: 120–121 The story first appeared as a fifty-four part serialisation in the London Evening News from Thursday, 16 July, to Wednesday, 16 September 1925 under the title Who Killed Ackroyd?

[29] Christie's dedication in the book reads "To Punkie, who likes an orthodox detective story, murder, inquest, and suspicion falling on every one in turn!"

[25]: 77 Margaret Watts wrote a play, The Claimant, based on the Tichborne Case, which enjoyed a short run in the West End at the Queen's Theatre from 11 September to 18 October 1924, two years before the book publication of The Murder of Roger Ackroyd.

"[15]: 277 In 2023, the novel was adapted for the stage by Edgar award nominated playwright Mark Shanahan[32] in partnership with Agatha Christie, Ltd.[33] The play received its first public reading at the Westport Country Playhouse in June 2023 with Santino Fontana as Dr. Sheppard and Arnie Burton as Poirot.

This world premiere adaptation elegantly transfers Christie’s rich mystery from the page to the stage..."[36] The play opened on 21 July and ran through 27 August in a limited run as part of the Alley Theatre's Summer Chills series[37] and was subsequently published by Concord Theatricals[38] before receiving numerous productions.

Cast: Orson Welles as Hercule Poirot and Dr Sheppard Edna May Oliver as Caroline Sheppard Alan Napier as Roger Ackroyd Brenda Forbes as Mrs Ackroyd Mary Taylor as Flora George Coulouris as Inspector Hamstead Ray Collins as Mr Raymond Everett Sloane as Parker The novel was also adapted as a 1½-hour radio play for BBC Radio 4 first broadcast on 24 December 1987.

Cast: John Moffatt as Hercule Poirot John Woodvine as Doctor Sheppard Laurence Payne as Roger Ackroyd Diana Olsson as Caroline Sheppard Eva Stuart as Miss Russell Peter Gilmore as Raymond Zelah Clarke as Flora Simon Cuff as Inspector Davis Deryck Guyler as Parker With Richard Tate, Alan Dudley, Joan Matheson, David Goodland, Peter Craze, Karen Archer and Paul Sirr The Murder of Roger Ackroyd was adapted as a 103-minute drama transmitted in the UK on ITV Sunday 2 January 2000, as an episode of Agatha Christie's Poirot.

[42] Adaptor: Clive Exton Director: Andrew Grieve Cast: David Suchet as Hercule Poirot Philip Jackson as Chief Inspector Japp Oliver Ford Davies as Dr Sheppard Selina Cadell as Caroline Sheppard Roger Frost as Parker Malcolm Terris as Roger Ackroyd Nigel Cooke as Geoffrey Raymond Daisy Beaumont as Ursula Bourne Flora Montgomery as Flora Ackroyd Vivien Heilbron as Mrs Ackroyd Gregor Truter as Inspector Davis Jamie Bamber as Ralph Paton Charles Early as Constable Jones Rosalind Bailey as Mrs Ferrars Charles Simon as Hammond Graham Chinn as Landlord Clive Brunt as Naval petty officer Alice Hart as Mary Philip Wrigley as Postman Phil Atkinson as Ted Elizabeth Kettle as Mrs Folliott The Murder of Roger Ackroyd was adapted as a 190-minute drama transmitted in Japan on Fuji Television on 14 April 2018, as a special drama, under the title "The Murder of Kuroido" (Japanese: 黒井戸殺し, Kuroido Goroshi).

This was translated from the edition first published in France by Emmanuel Proust éditions in 2004 under the title, Le Meurtre de Roger Ackroyd.