Three Act Tragedy

The novel opens at Crow's Nest, a modern bungalow overlooking Loomouth harbor in Cornwall, where Mr. Satterthwaite, a wealthy and keenly observant socialite, is the guest of Sir Charles Cartwright, a celebrated and recently retired stage actor. Sir Bartholomew Strange, a prominent London nerve specialist and Sir Charles's old Oxford friend, is also visiting and remarks that Sir Charles is perpetually acting, even off stage. That evening Sir Charles hosts a dinner party. Guests include Angela Sutcliffe, a well-known actress; Captain Freddie Dacres and his wife Cynthia; Muriel Wills, a playwright known publicly as Anthony Astor; Lady Mary Lytton Gore and her vivacious daughter Hermione, known as Egg; Oliver Manders, a young man working in his uncle's city firm; the Reverend Stephen Babbington and his wife; and Hercule Poirot, the Belgian detective.

During the cocktail hour, Babbington, a kind clergyman of about 60, sips his drink and grimaces. Moments later he rises, swaying and convulsed, and within two minutes he is dead. Sir Bartholomew urges caution about suspecting foul play, but Mr. Satterthwaite suggests having the cocktail glass analyzed. Poirot considers it improbable that anyone would murder a harmless old clergyman, noting the difficulty of directing a specific glass to a specific person. The analysis finds nothing but gin and vermouth.

Egg insists the death was murder. Mr. Satterthwaite recognizes that Egg is intensely attracted to Sir Charles, but Sir Charles believes she prefers Oliver. Convinced they belong together, he announces he is going abroad permanently. Egg is devastated and confesses she kissed Oliver only to provoke Sir Charles's jealousy.

Weeks later, Mr. Satterthwaite reads in Monte Carlo that Sir Bartholomew has died suddenly at his Yorkshire estate, Melfort Abbey, collapsing after drinking port in circumstances strikingly similar to Babbington's death. A newspaper report reveals a verdict of death by nicotine poisoning. Sir Charles appears with a letter from Egg begging him to return and investigate. Mr. Satterthwaite encounters Poirot, who concedes Sir Charles's instincts may have been right. All three return to England.

In Yorkshire, they learn the butler Ellis was hired only a fortnight before the murder and vanished the morning after. Nicotine was found in Strange's stomach but not in any glass or food. The guest list overlaps heavily with the Crow's Nest dinner. They theorize Strange assembled the same guests to test his suspicions about Babbington's death. Servants report Strange was in unusually high spirits on the fatal evening. In Ellis's room, Sir Charles deduces from an ink stain that Ellis hid papers behind the gas fire. They extract drafts of a blackmailing letter: Ellis witnessed something on the night of the murder. The letters prove he was not the murderer but knew who was.

Back in London, Egg proposes Ellis is dead, murdered because he knew too much. They discuss motives for Babbington's murder and settle on fear: Babbington may have innocently possessed dangerous information. Sir Charles and Egg visit Mrs. Babbington, who provides her late husband's biographical history. The Gilling, Kent years seem most promising for investigation. Lady Mary reports that Strange planned to "spring a surprise" on his guests.

Poirot arrives at Crow's Nest and agrees to hold a "watching brief," letting Sir Charles direct the investigation. They divide tasks among the suspects. Egg learns from a model at Mrs. Dacres's firm that the business is near ruin and that Strange may have interfered with one of Mrs. Dacres's schemes. Captain Dacres reveals he saw Miss Wills emerging from his room the morning after Strange's death. Sir Charles visits Miss Wills, who volunteers that Ellis had a strawberry birthmark on his left wrist. As Sir Charles leaves, he catches a look of "satisfied malice" on her face. Oliver claims Strange sent him a letter asking him to fake his motorcycle accident but says he destroyed it. A newspaper cutting about nicotine poisoning fell from Oliver's wallet in front of Miss Wills, though Oliver does not remember placing it there.

Poirot hosts a sherry party at the Ritz, inviting all the suspects. Sir Charles suddenly collapses as though dying. Poirot reveals the collapse was staged. In the moment every eye was on Sir Charles, Poirot switched the glass with a clean one, proving the murderer could have made the same substitution during each victim's collapse. This explains why no poison was ever found in the analyzed glasses. Privately, Poirot tells Sir Charles, Egg, and Mr. Satterthwaite he watched one person's face and saw "an expression of the utmost surprise." He claims to know the murderer but cannot prove it without understanding the motive. A telegram arrives from Mrs. de Rushbridger, a patient at Strange's Sanatorium, asking them to come.

At the Sanatorium, they discover Mrs. de Rushbridger has been murdered by nicotine-laced chocolates sent by post. The telegram was a forgery. At Gilling, Sir Charles and Egg visit Miss Milray's mother, who sits immovably in an armchair and provides no useful information. In the churchyard, Sir Charles reveals his real surname is Mugg, changed for his acting career, and he and Egg become engaged. When Egg mentions the "dress rehearsal" of Miss Wills's new play, Poirot has a breakthrough. He follows Miss Milray, Sir Charles's secretary, to Crow's Nest, where she climbs to a dilapidated tower containing chemical apparatus. She raises a crowbar to destroy the equipment, but Poirot stops her, telling her it is evidence.

Poirot assembles the group for his full solution. Sir Charles disguised himself as Ellis, using his actor's skills to impersonate a stooping, gray-haired servant with belladonna-darkened eyes and a painted birthmark. Strange knew about the disguise, believing it a joke, which explained his unusual teasing of the butler. After poisoning Strange's port, which Strange could not taste properly because influenza had damaged his senses, Sir Charles escaped through a secret passage and reappeared in Monte Carlo. The blackmail letters, Oliver's invitation to fake his accident, and the nicotine newspaper cutting were all planted by Sir Charles. Mrs. de Rushbridger was murdered to prevent investigators from discovering she knew nothing relevant. Miss Wills deduced the impersonation by recognizing that Ellis's hands matched Sir Charles's but kept silent. Miss Milray, secretly in love with Sir Charles, realized he had been extracting nicotine from rose-spraying solution in the tower and tried to destroy the evidence.

The motive: Sir Charles was already married to a woman who was a patient in a psychiatric institution and could not obtain a divorce. Strange, who had known Sir Charles since boyhood, would never have allowed a bigamous marriage to Egg. Babbington's murder was a "dress rehearsal." Sir Charles tested his method on a random victim to ensure the glass-switching technique would succeed. The nicotine could have killed anyone at the first dinner except Egg, to whom he handed a safe glass, himself, and Strange, who never drank cocktails.

Egg falls to her knees before Poirot and asks if it is true. Poirot confirms it gently. Sir Charles's face transforms, and he leaves the room. Poirot tells Mr. Satterthwaite that Sir Charles will choose his own exit. Oliver arrives and leads the devastated Egg to her mother. Mr. Satterthwaite realizes the poisoned cocktail at the dress rehearsal could have killed him, or, as Poirot notes, Poirot himself.