Following 2013’s Mama and 2024’s Mothers’ Instinct, Jessica Chastain returns yet again to the Matri-verse for one last job in Other Mommy, a demon horror about a not-so-imaginary, and not-so-friendly, imaginary friend. Directed by Rob Savage (Host, The Bogeyman) and written by Nathan Elston (based on Josh Malerman’s novel Incidents Around the House), Other Mommy is a fanciful, only occasionally spooky portrait of a young child processing domestic strife while being stalked by a nefarious entity.

It’s a clever conceit, to anthropomorphize a child’s sense that something is wrong in her family unit. All too often, it’s assumed that little ones aren’t able to perceive what’s happening around them, but of course they are osmosing information all the time and can be quite sensitive to ripples of discord and the furtive whisper of secrets even if they don’t fully understand their meaning. In the case of 7-year-old Bela (talented newcomer Arabella Olivia Clark), vague discord surrounds her parents’ marriage. Mom Ursula (Chastain) is busy with her career and mostly leaves the childcare to her husband, Russell (Jay Duplass), a fun-loving goof of a dad who seems a little sad in the presence of his wife. Ursula and Russell are tense and pinched around one another; a few context clues soon tell us what is ailing their union.

Because Ursula is often off doing mysterious things (like her job, and maybe something else), Bela entertains herself by talking and playing with something she calls Other Mommy, a spirit or demon of some kind who looks just like Ursula, but is more doting and loving than the distracted, chillier real thing. Well, at least we’re told that Other Mommy has been a good companion to Bela in the past. In the scope of the film, Other Mommy starts creepy and only gets more so. In that way, the film is missing a sense of dreadful build-up that might help its scares sink in deeper. As is, Savage’s film is an attractive but mostly vacuous collection of jumpy bits and half-baked mythology.

Other Mommy is capable of transporting people and objects to different places — across rooms and even further — but the entity only does so selectively, when narratively convenient. It’s never explained why Other Mommy has a sudden sense of urgency in getting Bela to agree to its request: that she let the monster (or whatever) into her heart. Presumably, Other Mommy and Bela have been hanging out for some time, but I guess OM was waiting for the cameras to start rolling to ramp up its campaign. Perhaps it senses that Ursula and Russell are at a breaking point, and soon enough Bela will have lost some of her innocence about family life and will thus make a less enticing host.

But that’s me being generous to the script, which hurriedly tosses off a few explanations and then continues its odd project of toggling between grave matters and arch comedy. The story does eventually arrive somewhere interesting — an acknowledgement that parenthood can be a taxing burden and was not always every parent’s dream for their life — but it’s a bumpy, silly road getting there. Maybe if the film had stayed closer to Bela’s perspective, doing something stylistically daring like David Mamet’s beguiling play The Cryptogram — which is told entirely in the stilted and half-grasped language of what a child overhears from a hidden distance — this would all have more resonance. But Other Mommy keeps things more straightforward than that, despite all the supernatural stuff swirling around this unhappy clan.

At least Chastain seems to be having fun in her role as the nefarious entity, flashing lots of menacing smiles and scraping and jittering around like she’s just come crawling out of Naomi Watts’ TV set. She also shrewdly adds necessary notes of flintiness and aloofness to Ursula’s bearing; it’s a sharp approximation of a parent who can be distant and withholding, and somewhat frightening for it. Or, if not frightening, at least unpredictable, a quietly unreliable and unknowable presence in the life of a needy child.

Credit must also be given to a few of Savage’s canny aesthetic flourishes. Sometimes he sends images reeling into incoherence, but just as often he blocks a scene and shoots it from a precise angle in a way that tells a neat, concise visual story. Especially striking is a shot-reverse-shot of father and daughter having a conversation as they peer at one another through a gap between large building blocks, separated by a literal wall and by a more metaphorical one, with looks of sad resignation on their faces. That lovely moment is soon interrupted by some nonsense involving a Chuck E. Cheese-style ball pit, but for a second there, Other Mommy takes on the affecting timbre of a grounded and thoughtful drama of childhood fantasy meeting difficult reality.

Other Mommy is somehow less engaging than the movie’s really well-cut trailer, a problem shared by a handful of films over the years. The ominous and awesome (in the old sense of the word) mood of the first Battle: Los Angeles trailer sadly gave way to a dumb, boring action movie. The suggested sweep and profundity of the gorgeous teaser for BIlly Lynn’s Long Halftime Walk went sadly unfulfilled in the actual picture. And now Other Mommy’s kicky first glimpse leads only to the disappointment of the film itself, an often eye-catching and well-performed whiff, one that’s neither poignant nor scary enough. Maybe there’s another movie, an Other Other Mommy, that could do the job better. I’ll be looking under my bed tonight trying to find it, likely in vain.