Hallowe’en Party (1969) is a mystery novel by Agatha Christie, one of the most famous mystery novelists of all time. It features Christie’s detective Hercule Poirot and mystery writer Ariadne Oliver, another recurring Christie character. In the novel, the murder of a 13-year-old girl named Joyce Reynolds leads Poirot to investigate several related crimes in the small town of Woodleigh Common.

Hallowe’en Party inspired the 2023 film adaptation A Haunting in Venice.

This guide cites the 2006 William Morrow e-book edition.

Content Warning: This guide references violence against children, discussion of sexual violence (including against children), stigma surrounding mental health conditions, death by suicide, and ritualistic/religious violence.

Plot Summary

Mystery novelist Ariadne Oliver attends a Hallowe’en party in Woodleigh Common, the small town she visits to stay with her friend Judith Butler. Mrs. Oliver’s fame causes Joyce Reynolds, another party guest, to brag that she witnessed a murder, but as Joyce is a notorious liar, nobody believes her. Later, Joyce is drowned in the bucket used to bob for apples. Though most locals consider this a random crime likely related to mental health concerns, Mrs. Oliver believes it to be a murder with an as-yet-unknown motive. She summons Hercule Poirot to help solve the case.

Poirot visits Woodleigh Common and interviews multiple villagers. He learns of Joyce’s reputation as a liar, as well as several other recent crimes, including one where an au pair named Olga Seminoff disappeared after producing a forged codicil to her late employer’s will that left Olga the woman’s vast estate. A forger named Lesley Ferrier was subsequently stabbed in the back. Poirot visits Quarry Garden, which was commissioned by Olga’s employer, Mrs. Llewellyn-Smythe. The gardener, Michael Garfield, still tends to the land. Poirot also meets Miranda Butler, Judith’s daughter, who likes to visit the garden. (He later learns that Miranda was the true witness to the murder Joyce claimed to have seen, passing Miranda’s experience off as her own to impress Mrs. Oliver.)

Another of Mrs. Llewellyn-Smythe’s former employees visits Mrs. Oliver to report that she witnessed the signing of a real codicil that left everything to Olga. They later learn that there was both a real and a fake codicil; Michael Garfield commissioned the latter to cast doubt on Olga’s inheritance so that Mrs. Drake, his lover, would inherit her aunt’s estate. Poirot overhears Miranda asking about a wishing well, which Michael discourages her from finding. Poirot later reveals this is where Michael and Mrs. Drake hid Olga’s body after framing her for forgery and killing her. Poirot receives news that somebody (later revealed as Mrs. Drake) killed Leopold Reynolds, who had been blackmailing the murderers because he knew what Miranda had seen, though he believed Joyce the true witness.

Poirot directs the police to look for the wishing well in which they find Olga’s body and the knife used to kill Lesley Ferrier. Poirot recognizes that Miranda must be the true witness, given her propensity for sitting quietly in the woods. He urges Mrs. Oliver to bring Miranda and Judith Butler to London, where they will be safe from Michael Garfield and Mrs. Drake, the conspirators in the killing. Miranda, who is fond of Garfield, tells him about her plans and willingly goes with him to be “sacrificed” at standing stones. Miranda feels she deserves to be sacrificed for telling Joyce the story about witnessing a murder that led to Joyce’s death. Just as Michael is about to poison and stab Miranda, two adolescent boys from the village, Desmond and Nicholas, interrupt, saving Miranda. Michael drinks the poison himself and dies by suicide.

Poirot gathers Miranda, Mrs. Oliver, Mrs. Butler, and the police to explain the crime. Several years prior, Michael attempted to seduce his elderly employer, Mrs. Llewellyn-Smythe. When this failed, he sought a relationship with Mrs. Drake, Mrs. Llewellyn-Smythe’s recently widowed niece, who was the primary heir of the estate. Michael, obsessed with the idea of creating an idyllic garden on a remote, uninhabited Greek island, wanted the money to make this dream a reality.

When Mrs. Llewellyn-Smythe learned of this affair, she wrote the initial codicil, which left everything to Olga. When the elderly woman died, Michael hired Lesley Ferrier to make an obviously forged codicil, to cast Olga’s story into doubt. He and Mrs. Drake then killed Olga to make it seem as though she disappeared to avoid prosecution for the false document. Miranda, hiding in a tree, saw them moving Olga’s body, but she did not recognize it immediately as a murder.

Once Miranda realized the truth of what she’d seen, she confided only in Joyce, as she wished to have something impressive to tell her friend. Miranda was the only one who believed Joyce’s fantastical tales. Leopold overheard Miranda telling Joyce about what she had seen. When Joyce bragged about witnessing a murder, Mrs. Drake killed her. When Leopold blackmailed her with the knowledge of what his sister had seen, Mrs. Drake killed him, too.

Mrs. Butler explains that Michael Garfield is actually Miranda’s father; her daughter was the result of a short-lived affair between the two when Judith was young. They ended up in Woodleigh Common together entirely by chance. Poirot knows this; he produces a sketch Michael made of Miranda, which he has titled “Iphigenia,” referencing a character from Greek myth who is sacrificed by her father. Poirot takes this as evidence that, even knowing Miranda’s parentage, Michael would have killed her anyway, as part of his fervent desire to build an enormous garden on the Greek island he and Mrs. Drake had purchased; the bill of sale proves the concrete evidence linking Mrs. Drake to the crimes.