Hallowe'en Party

While visiting her friend Judith Butler in Woodleigh Common, Ariadne Oliver assists the neighbours in planning a children's Hallowe'en Party at wealthy Rowena Drake's house. Upon meeting Mrs Oliver, 13-year-old Joyce Reynolds claims she once witnessed a murder, though at the time she was too young to realise. Despite no one appearing to believe her, Joyce is found drowned in an apple-bobbing bucket after the party; distraught, Mrs Oliver summons Hercule Poirot.

With help from retired Superintendent Spence, Poirot makes a list of recent deaths and disappearances in the area of Woodleigh Common. Of these, three stand out as significant:

• Rowena's aunt, Mrs Llewellyn-Smythe, died suddenly, but of what was believed to be natural causes.
• Her au pair, Olga Seminoff, disappeared when a codicil that favoured her in her employer's will was found to be a forgery.
• Leslie Ferrier, a lawyer's clerk with unsavory connections and prior convictions for forgery, was stabbed in the back by an unknown assailant.

Interviewing the townsfolk, Poirot learns a few interesting facts:

• Judith's daughter, Miranda, was Joyce's closest friend, and the pair shared secrets.
• Joyce was known to lie to get attention.
• Elizabeth Whittaker, a mathematics teacher, witnessed Rowena become startled and drop a vase of water outside the library while the party-goers were playing snap-dragon.
• A one-time cleaner of Mrs Llewellyn-Smythe had been witness to her employer making the supposedly forged codicil.
• A beautiful garden built within an abandoned quarry was designed by Michael Garfield, a handsome narcissistic man, for Mrs Llewellyn-Smythe. He lived in a lodge on the grounds to oversee the work, and still lives there.
• The victim's brother, Leopold Reynolds, has become flush with money of late.

Leopold is found dead. Rowena informs Poirot that she had seen him in the library the night of the party, and she believes he witnessed his sister's murder.

Poirot advises the police to search the woods near the quarry. The search finds Olga's body in an abandoned well, stabbed in the same manner as Ferrier. Fearing another murder, Poirot sends a telegram to Mrs Oliver, instructing her to take Judith and her daughter to London.

Miranda meets with Garfield, who takes her to a pagan sacrificial altar, intending to poison her. However, he commits suicide when two youths recruited by Poirot save Miranda's life. Miranda reveals that she was the one who saw Garfield and Rowena drag Olga's body through the quarry garden, and she secretly told Joyce. Miranda had not been present at the preparations for the party, so Joyce tried to seek famous Ariadne's attention by claiming Miranda's story as her own.

Poirot lays out the solution to Mrs Oliver and Mrs Butler. Rowena began an affair with Garfield while her dying husband was still alive. Disgusted by this, Rowena's aunt wrote a codicil that left her fortune to Olga. The lovers then plotted to discredit Olga's claim, hiring Ferrier to replace the codicil with a deliberately clumsy forgery to ensure Rowena inherited everything; the real codicil has now been found by the police. Both Olga and Ferrier were murdered to conceal the deceit, but Rowena suspected someone had witnessed the disposal of Olga's body. Rowena killed Joyce when she claimed she had witnessed a murder, unaware that Joyce had appropriated Miranda's story. The dropping of the vase, which Mrs Whittaker witnessed, was to disguise the fact that Rowena was already wet from drowning Joyce. Leopold was murdered because he asked Rowena for money, and she suspected he knew something.

Poirot muses that Rowena likely would have shared a similar fate to Olga, as Garfield's motivation for the murder was his obsession with constructing a second, more perfect garden. Once he had Rowena's money, he would soon have no more need of her, as she had already provided him with a Greek island.

Poirot also reveals that Judith is not really a widow. She once had a brief affair with Michael Garfield, and Miranda is the child of that union. The Butlers met Michael again by chance years later; though fond of Miranda, Michael was willing to kill his own child to satisfy his need to create. Satisfied with Poirot's help, Judith thanks him.