Jessica Chastain playing semi-dual roles in a twisted supernatural horror film was more than enough to spark my interest. If only “Other Mommy” offered her better material to work with. Instead, the Academy Award-winning Chastain finds herself held captive by a movie that lacks the intrigue, suspense, and scares found in its very own trailer. It’s an astonishing misfire and easily one of the more disappointing horror films of the year.

“Other Mommy” is based on the 2024 novel “Incidents Around the House” by Josh Malerman. It’s adapted for the screen by Nathan Elston who attempts to combine supernatural horror with a domestic drama. Unfortunately neither works, either together or on their own. That’s because we never get more than a surface-level connection with the family. And while director Rob Savage devises some delightfully gory jolts, the horror elements fall short simply because there is so much that doesn’t make sense.

As for the story, Ursula (Chastain) is a successful businesswoman who seems to have a perfect life. She’s married to Russ (a miscast Jay Duplass) who takes care of the house while she advances her career. Together they have a darling 7-year-old daughter named Bela (Arabella Olivia Clark) who is trying her best to adjust to her new school. But we quickly begin to notice cracks in Ursula and Russ’ marriage. Bela notices it too, which leaves her vulnerable to the wooing of an evil entity.

Bela begins having encounters with a supernatural presence that takes the form of Ursula. Bela names her Other Mommy and is slowing lured in by the entity’s twisted charms. Other Mommy repeatedly asks “Let me into your heart”, which Bela is reluctant to allow. As the entity grows impatient, its aggression intensifies. And before long it’s not just preying on Bela, but their entire family as well. That forces Ursula and Russ to patch up their differences in order to protect their daughter.

Now there’s nothing wrong with that setup, and it sets the table for what could have been a tense and terrifying story. But after its promising start, the movie trudges from one semi-spooky encounter to the next with nothing remotely interesting connecting them together. Several other players are thrown in including a family friend named Frank (Arian Moayed), Ursula’s estranged mother (Karen Allen), and a team of paranormal investigators. But most exist solely as fodder for Other Mommy.

As mentioned, the entity does get a few creepy moments and there is at least one memorably gruesome kill. But Savage’s overreliance on tired clichés and mediocre CGI holds other scenes back. Plus it’s hard to invest when the ‘rules’ of the entity are never defined. Chastain certainly does her part, putting maximum effort into both of the characters she plays. She truly keeps the movie afloat with the subtle volatility she hides inside of Ursula and the dark menacing edge she brings out of Other Mommy. Chastain is quickly established as the film’s biggest strength.

Yet despite its star’s admirable commitment, “Other Mommy” can’t overcome its drab storytelling and glaring lack of originality. There are some rich themes caught in the film’s narrative gears, and there are several times when we’re reminded of what the movie could have been. But even the most faithful horror fans are liable to find themselves baffled by the tedium. And like the rest of us, they’ll find the only thing harder than staying engaged will be staying awake.