If you've seen the short film that ultimately grew to become Mama, you have a good idea of what to expect. Stretched out to an hour and a half, that tone sustains. Make no mistake, on the primal level that it needs to, Mama works one hundred per cent; I can't recall being this scared in a movie since the heyday of J-horror. That there are plot points to argue with afterward is secondary - you can't fake fear, and Mama brings it. So yes, Guillermo del Toro still knows what he's doing as "presenter," whatever that means (compare him to, say, Wes Craven, who will "present" anything - like Dracula 2000 - that helps to fund his next project).
The best horror always takes real-life fears and gives them a spin, and here we are dealing with several. The first, and silliest, ties in to our financial crisis: as we hear in radio broadcasts that the stock market has taken yet another colossal dump, Wall Street player Jeffrey (Nikolaj Coster-Waldau) shoots and kills his wife, then drives his two young daughters out into the wilderness, where he crashes the car due to his preoccupation with yelling at them. Finding an isolated, uh, cabin in the woods, (cue program #WhateverTheFuck, Richard Jenkins and Bradley Whitford), he plans to shoot his daughters and then himself, but before he can execute part one, his neck gets snapped. Spoiler complainers, let's get serious: you really thought the mainstream movie was going to allow kindergarteners to get knocked off? Don't be silly. This is actually quite the metaphorical fairy-tale set-up, not unlike Snow White and the huntsman, but completely unlike the god-awful movie that was actually called Snow White and the Huntsman.
A couple of years later, the girls are found, but they're wild, animalistic, and talk to the wall. Jeffrey's brother Lucas (Coster-Waldau again, but with facial hair this time) wants to take them in, against the wishes of his goth-rocker girlfriend Annabel (Jessica Chastain, at maximum hotness with a black dye-job and octopus tattoos) who's terrified of motherhood. Though the kids' nasty aunt (Jane Moffat) wants custody, and points out the young couple's financial inadequacies, Lucas and Annabel make a deal with creepy, Monk-like Dr. Dreyfuss (Daniel Kash, whose first major acting role was as Private Spunkmeyer in Aliens) to move into a house used for case studies rent-free, where he can observe the girls' progress.
Now, as the trailers and everything else have made abundantly clear, the girls have a supernatural guardian named "Mama" who's less than benevolent towards anyone else. Heralded by a flurry of moths, she sneaks in at night, unseen, and watches over her "children." Director Andres Muschietti expertly builds tension in scenes where we think we see one of the girls playing tug-of-war with her sister, only to have the other girl enter frame and make us realize an invisible force is there; or show a girl's legs up in the air, in an unfeasible position; or have us think Annabel is seeing one of the girls, only to make it clear that both are out of frame and she must be looking at someone (or something) else. Muschietti rather perfectly delivers that balance of giving us just enough of a look (enhanced by modern effects) at the scary thing while keeping it sufficiently offscreen to make us imagine what it might be - then ultimately delivering a terrifying creation to match what we feared, like a Ringu-style Blair Witch finally revealed. It's a tough trifecta to hit, but he nails it.
The "don't look in the closet" and "don't look under the bed" moments may be sublime, but I do have to call the characters out on one significant point: why, after they realize Mama is real and malevolent - as opposed to an external split-personality belonging to one of the girls - does more than one character decide to pay a visit to her spooky cabin...alone...at night? Jeez, you might as well bring your sexy drug dealer to bang and get high at the same time; at least you'll die happy.
And Mama's intellectual capacity leads to some uncomfortable questions - she can instantly find the girls she seeks, but another thing that she's looking for is right under her nose, and she misses it; that her appearance suggests a mental handicap like Down's Syndrome may be problematic for some, as "explanation" for why her angry spirit just doesn't get it at several points. On the other hand, you can argue that the mentally challenged should be allowed representation across the full spectrum of characters, including malevolent ghosts. If you're wondering how to explain it all to your kids let me be clear: DON'T TAKE YOUR KIDS. Unless you love dealing with night terrors.