Other Mommy Is Based on Incidents Around the House — What Jessica Chastain's Horror Movie Is Adapting

Yes. Other Mommy is a film adaptation of Josh Malerman’s 2024 horror novel Incidents Around the House. Universal retitled the movie after the name its young protagonist gives the entity in the story, but it is adapting Malerman’s book — not an unrelated film with a similar premise. It opens in U.S. theaters on October 9, 2026.

Jessica Chastain stars in a dual role as Bela’s mother and Other Mommy, while Rob Savage directs from a screenplay by Nathan Elston. James Wan produces for Blumhouse Atomic Monster. Those are the confirmed basics; exactly how closely the finished movie follows every event in the novel has not been established ahead of release.

What book is Other Mommy based on?

The source is Incidents Around the House, Malerman’s 2024 novel, published by Del Rey. Penguin Random House describes it as the story of eight-year-old Bela and her troubled family, haunted by an entity Bela calls Other Mommy. The publisher’s page now explicitly bills it as the major motion picture Other Mommy, starring Chastain.

That makes the title relationship unusually straightforward. Incidents Around the House is the book title; Other Mommy is the name used for the story’s central entity. Universal has not publicly explained why it chose that name for the film title, so it is better to treat the retitle as a fact of the adaptation rather than assign a marketing reason to it.

The book’s premise is deliberately child-centered. Bela’s immediate world is Mommy, Daddo and Grandma Ruth — and the unnerving presence that repeatedly asks to go inside her heart. That setup explains the movie’s focus on a child, a family home and a mother-shaped threat without requiring a spoiler-heavy account of where the novel goes.

What is the movie’s confirmed setup?

Universal’s official synopsis stays close to that basic frame. Bela forms a relationship with a sinister entity in her home that looks uncannily like her own mother. Chastain plays both Bela’s mother and “Other Mommy,” which Universal calls a manifestation of the entity.

That wording matters. The studio has confirmed a mother-like manifestation, but it has not provided a final taxonomy for the entity. Calling Other Mommy a demon, ghost or alien before the film defines it would go beyond the material Universal has released.

The October 9 date is a theatrical release date. Universal’s upcoming slate lists Other Mommy as arriving in theaters that day; it has not announced a streaming release plan in the official materials used for this guide.

Who is making Other Mommy?

Rob Savage directs, and Nathan Elston wrote the screenplay. Universal identifies the production as a Blumhouse Atomic Monster film, with James Wan as producer. Wan is not the director of Other Mommy — a distinction worth making given his association with several major horror franchises. For context on one of those series, see our guide to Insidious: Out of the Further.

Universal also lists Michael Clear, Judson Scott, Savage, Malerman and Ryan Lewis as executive producers. Malerman’s involvement as an executive producer is confirmed, but that credit alone does not tell viewers which book material the film keeps, changes or expands.

Other Mommy cast: who plays whom?

The official character assignments are compact:

• Jessica Chastain as Bela’s mother and Other Mommy
• Arabella Olivia Clark as Bela
• Jay Duplass as Daddo, Bela’s father

Dichen Lachman, Arian Moayed and Karen Allen are also in the supporting cast. Universal has not assigned public character names to those three in its synopsis, so there is no reason to fill in roles from unverified listings.

The dual casting is the movie’s clearest adaptation-facing change in emphasis that Universal has made public. The studio’s own setup invites viewers to understand the entity through its resemblance to Bela’s mother; it does not, however, reveal the full mechanics of that resemblance or resolve the family’s conflict before the film opens.

What is known about the book-to-film changes?

Very little, and that is the right answer before release. The film is officially based on Incidents Around the House and preserves Bela, Other Mommy, Mommy and Daddo in its public-facing premise. Its trailer and synopsis also establish Chastain’s dual role.

Beyond that, trailer omissions are not evidence of adaptation changes. A novel’s events may be held back for a film’s marketing, reordered for a screenplay or simply not discussed publicly. There is no reliable basis yet to label the movie a faithful, loose or page-by-page adaptation.

Readers who want to go in as fresh as possible can take away the useful distinction: Other Mommy is not a new James Wan-directed original. It is Savage’s film version of Malerman’s book, produced by Wan, and its title foregrounds the entity at the center of Bela’s story.

What remains unknown before October 9?

Universal has confirmed the cast, creative team, theatrical date and core premise. It has not confirmed an episode-like breakdown of the story, a streaming date, or a detailed guide to changes from the novel. It also has not stated why the adaptation was retitled.

Those gaps are worth preserving. A spoiler-light pre-watch guide should explain the connection to Incidents Around the House, not turn unannounced plot choices into promises. For more supernatural-horror context from Wan’s producing orbit, our guide to Valak and the Conjuring Universe maps a different franchise without implying the films share continuity.

Other Mommy opens in theaters October 9, 2026.