Hey everyone, let's play a fun game I invented, called "Being Jessica Chastain". Pretend it's late 2011, and you are a 34-year-old actress who has gone from complete anonymity to ubiquity in the blink of an eye. You've already been in the year's best-reviewed art film, and you're one of the most-praised members of the ensemble cast of one of the year's biggest surprise box-office smashes. You're scheduled, in a couple of months, to shoot Kathryn Bigelow's much-anticipated follow-up to the Best Picture Oscar-winning The Hurt Locker. The game is this: explain what in Christ's green and growing earth made you decide to play the lead role in a seedy little horror flick like Mama. Are you playing genre film bingo? You already had "aesthetically dubious message movie", "nervy character-driven indie", and "milquetoast action film", and you needed "paint-by-numbers PG-13 horror film" to win? I beg someone to explain this to me, for I truly do not understand it.

Chastain's performance, if you've seen enough of her other work - and I imagine that most of us have, by now - is actually quite a terrific piece of chameleonoid gamesmanship, and not just because she's hidden her wonderful wavy red mane beneath a severe black wig and rendered herself nearly unrecognisable in the process. While Chastain is not mine, nor I expect most people's idea of a surly punk chick - an early scene that witnesses her rocking out on bass suggests, at a minimum, that the actress had never touched a guitar before that morning on set - she nails the insouciant attitude and "fuck it all" weariness implied by that character type real damn well. The fascinating thing is that, if you just take the movie in itself and don't realise how massively far afield she is from anything else she's done so far, her performance actually seems quite forced and dreadful, indistinguishable from any one of a hundred similar performance in similar movies where stilted, hyper-enunciated line readings and a heavily self-conscious physical bearing are the name of the game. Are we witnessing a conscious attempt to mimic the behavior of shlocky horror by a performer capable of more, in some kind of odd obedience to the rich tradition of predictable, countdown-to-the-jump-scare ghost stories? God knows.

It would make sense, actually, if that was the case, because Mama, as a whole, feels like people who could be making a much better film spending too much time playing in the same old sandbox as everybody else. For there is atmosphere aplenty in this, the debut feature of one Andrés Muschietti (co-writing with his sister, Barbara, as well as Neil Cross), working under the sheltering wing of executive producer Guillermo del Toro (whose fingerprints are not nearly as evident as in e.g. Don't Be Afraid of the Dark, until the wildly misjudged fairy tale ending), and that atmosphere generally works to make one awfully susceptible to the various jump scares, even as they appear with metronomic consistency. It works, indeed, even as the film's delirious eagerness to let us know pretty early on exactly what is happening commits the common sin of domesticating the horror and making it less unfathomable and thus less scary. For every great moment of creeping dread, then, there is a patch of truly unforgivable screenwriting, whether because of its allegiance to the worst kind of horror contrivance (the number of "how stupid do you have to be go in that closet/house/dark hallway" moments is truly magnificent here), or simply for missing a chance to do something really incredible; Mama has the makings of a really nifty psychological horror experiment, but far too readily sacrifices character for a quick jolt of adrenaline. It also keeps making the same exact mechanical error over and over again, which is that it's completely arbitrary about its point of view; see; only some characters can see the titular ghost Mama (the lanky and angular Javier Botet), and sometimes, the film decides to use their POV to take advantage of that fact, solely for the benefit of making the viewer squirm, not because that POV is justified by the script in any way. It's a little cheat, but one that the movie leans on awfully hard.

So anyway, Mama opens at the very start of the 2007-'08 financial crisis (and boy, does it not earn it), as a man kills his wife and takes his two very young daughters into the Virginia woods, to kill them too. But before he can, a necrotic ghost kills him, and raises the children as its own. Five years later, they are found, on the very last drop of money that their uncle Lucas (Nikolaj Coster-Waldau, who also briefly plays their dad) had to spend. He excitedly takes them in, doing a bit of ethically dubious soft-shoeing with psychologist Dr. Dreyfuss (Daniel Kash) to make sure that the girls are kept where the doctor can keep studying them; this is all not very exciting for Lucas's rocker girlfriend Annabel (Chastain), who finds the rough, unpolished 8-year-old Victoria (Megan Charpentier) and the positively feral 6-year-old Lilly (Isabelle Nélisse) to be exactly the children she never wanted (she's introduced celebrating a negative pregnancy test). The fact that the girls have carried the ghostly Mama along with them, naturally enough, makes matters worse, particularly as Annabel begins to break through to Victoria, thus rousing the spirit's maternal jealousy.

Mama's secret isn't nearly complex enough, nor buried enough, to be a spoiler, but I'll leave it alone; suffice to say that it's a lot weirder and creepier the less we know, and it's certainly scarier the less we see: when the ghost is a shadowy black collection of impossible limbs hanging out, unseen, in windows, she's enough to raise all the little hairs on your arms and neck, and even when we see her face just enough to make out the cloudy, malice-filled eyes, the monster design is more than enough for a rock-solid jump scare. Unfortunately, as the movie proceeds, Mama is more and more a character, and by the one-hour mark, the filmmakers aren't trying to hide her at all: and the more we see of her, the more she resembles an anorexic troll from the Lord of the Rings films, and not a tormented avatar of undead rage.

The film makes no new mistakes, and so can hardly be called surprising; and when it is not indulging in narrative and visual clichés, it is a genuinely effective mood piece; Chastain proves to be a damn good screamer, and the little girls are uncanny enough, just staring with animalistic emptiness, that when the movie is all about how hard it is for their ad hoc new stepmother to figure out what to do with them, it is genuinely unsettling. So why couldn't the film have been about that, instead of yet another "restless spirit with an easily-resolved torment that the characters could have dealt with half the movie ago, if they had any imagination or intelligence at all" stock narrative? Instead, we get a film that is intermittently frightening, often just overbaked with images of rot and gloom, and not remotely fresh or interesting. It's too good a work of foreboding mise en scène to be a film about jump scares happening to dumb people; and yet that is all that it wants to be. A damned pity, for we need better atmospheric horror.