The movie A Haunting in Venice is loosely based on the 1969 Agatha Christie novel Hallowe’en Party , not a direct adaptation but an inspired‑by version.

What book it’s based on

  • The film credits and studio materials list Hallowe’en Party by Agatha Christie as the source novel.
  • Screenwriter Michael Green has described the project as “inspired by” the book rather than a faithful adaptation, more like a re‑imagined ghost‑story take on it.

How different is the movie?

  • While both involve Poirot, mystery writer Ariadne Oliver, a Halloween‑set party, and a series of deaths, the screen version swaps the English‑village setting for a haunted palazzo in post‑war Venice and leans much more into supernatural horror.
  • Fans of Christie’s original note that plot details, motivations, and even some character arcs are substantially changed, so Hallowe’en Party functions more as a rough template than a blueprint.

If you’re curious, reading Hallowe’en Party will give you the “classic” version of the story, while A Haunting in Venice is a darker, more atmospheric spin‑off in the same universe.