Other Mommy opens with new deaths and a different ending from the book

Other Mommy is now playing in theatres with an ending book readers will not recognise.

Universal Pictures released the horror film on 9 October, according to Universal Pictures. The story is based on Josh Malerman's 2024 novel Incidents Around the House, and stars Jessica Chastain as mother Ursula and Arabella Olivia Clark as her young daughter Bela, according to Variety. That outlet has gathered the five biggest differences between page and screen.

The film arrives with strong commercial expectations. It was projected to open at No. 1 at the U.S. weekend box office with around $20 million, Deadline reported on 7 October. A separate preview put the opening range at $17 million to $22 million in the United States and Canada, according to Box Office Pro.

One change concerns family friend Frank, played by Arian Moayed. In the film, the creature called Other Mommy kills Frank in front of Bela by making his head explode. In the book, there is no on-page killing. Ursula simply tells Bela that Frank was found dead in a closet.

Another change centres on the séance. In the film, Grandma Ruth, played by Karen Allen, organises the ritual. It ends in bloodshed when Other Mommy kills a team of ghost hunters. In the book, the séance is arranged very differently. Two self-described spiritualists turn up, then admit they cannot help and leave.

The ending itself is rewritten. In the film, Bela refuses to let Other Mommy into her heart. That refusal defeats the demon. The family of three survives intact.

The book goes further. In Malerman's final pages, the demon kills Grandma Ruth and then takes her shape. Bela is left with a new, crueller version of Other Mommy wearing her grandmother's form.

For fans going in fresh, this means the central question is the same but the answers differ. Bela can hear and see the entity. Her parents cannot. The film keeps that divide, then gives Bela a clearer power to say no.