Other Mommy brings Josh Malerman's 2024 novel Incidents Around the House to the screen. The adaptation preserves the book's most recognizable core: Bela, an eight-year-old girl, lives in a family under strain and begins dealing with a threatening presence inside her home that she calls Other Mommy.
Universal Pictures lists the theatrical release for October 9, 2026 and confirms Jessica Chastain in two roles: Bela's mother and the manifestation of the entity known as Other Mommy. That choice makes a visual connection explicit, while the novel treats the creature as something stranger and more ambiguous than a simple "replacement mother."
What Other Mommy adapts from Incidents Around the House
The starting point comes directly from the novel. According to the official Penguin Random House synopsis, Bela lives with Mommy, Daddo and Grandma Ruth, but she also encounters a malevolent entity that repeatedly asks to enter her heart. The threat intensifies as Bela refuses, while problems within the family weaken the child's sense of safety.
The film keeps that central setup. Universal's synopsis describes Bela forming a relationship with a sinister entity in her home and confirms that the creature looks uncannily like her own mother. The released material therefore does not suggest an adaptation that discards the book's premise or replaces its central characters with an unrelated story.
Jay Duplass is also confirmed as Daddo and Arabella Olivia Clark as Bela. Dichen Lachman, Arian Moayed and Karen Allen are part of the supporting cast. Rob Savage directs, Nathan Elston wrote the screenplay, and James Wan produces the film through Blumhouse Atomic Monster.
Who Other Mommy is in the novel
The key fact for understanding the character is that Other Mommy does not have a fully explained, objective origin in the published material. The novel presents her as a malevolent, nonhuman entity but keeps the mystery around what she is, where she came from and what specific supernatural category might describe her.
Josh Malerman discussed that ambiguity in an interview with This Is Horror. He explained that the name should not be taken as proof that the creature is literally another mother or a replacement for Bela's mother. The logic is rooted in a child's perception: Bela gives a familiar name to something that is not a person and whose appearance can suggest a maternal figure to her.
That changes how the entity should be read. Rather than starting with an origin story, the novel works through invasion, persistence and uncertainty. The horror comes from both the physical presence and the repeated question directed at Bela, along with the possibility that the entity might cross a boundary the child is trying to maintain.
Why Jessica Chastain plays both the mother and the entity
Universal confirms Chastain as Bela's mother and as the manifestation of Other Mommy. The decision creates a clear cinematic equivalence: viewers can recognize the resemblance immediately while the film can still preserve uncertainty about what lies behind that appearance.
In a recent interview with Entertainment Weekly, Rob Savage described Chastain's performance as central to differentiating the two presences. The director also said the film's opening is taken directly from the book. That is concrete evidence of fidelity to specific material, but it does not prove that the entire structure, every family relationship or the ending remains unchanged.
What is already confirmed about the adaptation
- The film is based on Josh Malerman's Incidents Around the House.
- Bela remains the child at the center of the story.
- Other Mommy remains an entity tied to the house and to Bela's experience.
- Jessica Chastain plays both the mother and the entity's manifestation.
- Jay Duplass plays Daddo and Arabella Olivia Clark plays Bela.
- Rob Savage directs, Nathan Elston wrote the screenplay and James Wan is a producer.
- Universal lists the theatrical release for October 9, 2026.
What cannot be confirmed until the film is released
The official material is enough to understand the premise, cast and visual approach to Other Mommy, but it does not settle every adaptation question. Before release, it is not safe to claim that the film explains more about the entity's origin, keeps the same level of ambiguity as the novel or leaves major events from the second half unchanged.
The degree of fidelity can only be assessed after comparing the complete film with the book. That includes how the movie translates Bela's child perspective, how much weight it gives the parents' conflicts, the function of supporting characters, the rhythm of the manifestations and the treatment of the ending.
So who is Jessica Chastain's entity?
Based on what is confirmed so far, the most precise answer is: Other Mommy is a manifestation of a nonhuman supernatural entity that approaches Bela and takes on an appearance resembling her mother. In the novel, her origin remains deliberately undefined. In the film, Chastain embodies both the mother and the form used by the entity, making the confusion and threat visually immediate.
The open question is what may ultimately distinguish the adaptation: whether the movie preserves the novel's mystery or adds a more concrete explanation. Until release, any firmer answer about Other Mommy's origin should be treated as interpretation rather than confirmed fact.
