Lord Edgware Dies

Attending a performance by impressionist Carlotta Adams, Hercule Poirot is approached by actress Jane Wilkinson. She requests his help in asking her husband, Lord Edgware, to divorce her. Although a Catholic, Poirot agrees but is surprised to learn Edgware has already agreed to a divorce and sent a letter to his wife confirming this; Wilkinson denies receiving it. The following morning, Inspector Japp informs Poirot and his friend Arthur Hastings that Edgware had been murdered at his home in Regent Gate the previous evening, stabbed in the neck. While Wilkinson was witnessed by Edgware's butler and his secretary visiting her husband that night, a morning newspaper reveals she attended a dinner party the same evening, and other guests confirm this. Poirot soon becomes concerned for Adams' safety, recalling she could impersonate Wilkinson. Adams is found dead that same morning from an overdose of Veronal.

Seeking answers, Poirot notes a few facts: Bryan Martin, a former lover of Wilkinson before she met the wealthy Duke of Merton, bitterly describes her as an amoral person; Donald Ross, a guest at the party, witnessed her take a telephone call from someone that night; Adams possessed a pair of pince-nez, along with a gold case that contained the drug, which has a puzzling inscription in it; Edgware's nephew, Ronald Marsh, had been cut off from his allowance by his uncle three months earlier; a sum of francs formerly in Edgware's possession has disappeared, along with the butler. Learning Adams had sent a letter to her sister in America before her death, Poirot makes a request for it. A copy is sent via telegram, revealing Adams was offered $10,000 for an undisclosed endeavour. Poirot suspects she was hired to impersonate Wilkinson.

Japp soon arrests Marsh, based on this letter. Marsh denies hiring Adams or killing his uncle but states that he and his cousin Geraldine went to Regent Gates on the night of the murder, where he spotted Martin entering the house although Geraldine did not as she was retrieving something for him. Poirot later receives the original letter in the post and notes some oddities with it. Hastings attends a luncheon party along with Wilkinson and Ross, in which the guests talk about Paris of Troy. Wilkinson presumes they are talking of the French capital and begins discussing fashion. Ross, puzzled by this, considering how clever Wilkinson had been the last time he met her, confides his concerns to Hastings. He later telephones Poirot but is fatally stabbed before he can explain in detail. Seeking a theory, Poirot overhears a chance remark from a crowd leaving a theatre, which leads him to talk with Ellis, Wilkinson's maid.

Gathering the suspects together, Poirot reveals that the killer in all three murders is Jane Wilkinson. Her motive in killing Lord Edgware is that the devout Duke of Merton would not marry a divorced woman. A widow, however, is a different matter. She recruited Adams to impersonate her at the dinner party, while she killed her husband and then killed Adams afterwards with a fatal dose of Veronal. The women met at a hotel to exchange clothing before and after the party. While waiting for Adams to return from the party, Wilkinson discovers a letter among Adams's belongings that had yet to be posted and tampers with the letter to implicate the last man it mentions for the murders. Ross was killed because he realised that Wilkinson did not attend the dinner party; her ignorance of Greek mythology gave her away, as Adams had been knowledgeable on the subject and thus talked about it while impersonating her.

Poirot reveals what led him to his theory: Wilkinson lied about receiving her husband's letter and used Poirot to prove she had no motive for his murder; the telephone call to Adams was to confirm if their deception had yet to be exposed; the pince-nez, belonging to Ellis, used in a disguise that she and Wilkinson wore to keep their hotel meetings secret; the gold case was created a week before the murder, not six months as its inscription implied - Wilkinson had it made under a false name and then sent Ellis to collect it; a corner of a page in Adams' letter was torn by Wilkinson, changing the word "she" to "he", to imply that a man hired Adams. Poirot reveals that the butler stole the missing money; Marsh had witnessed him entering Regent Gates to hide it elsewhere; his disappearance was because he panicked when the police sought another suspect.

Wilkinson is arrested and writes to Poirot from prison about wishing an audience for her hanging, surprisingly evincing no anger at being foiled by him - nor any remorse.