This horror film, the first feature by brother-and-sister team of Andy and Barbara Muschietti, is as stylish as you’d expect of a project on which Guillermo del Toro served as executive producer. A good deal of the imagery, like the swarms of moths and butterflies, is reminiscent of his pictures. But though it’s visually elegant—with cinematography (by Antonio Riestra that artfully employs smooth tracking shots—and boasts some genuinely creepy moments, it’s narratively thin and repetitive, and relies too much on “gotcha” moments that quickly grow tiresome.

The script, developed by the Muschiettis and Neil Cross from the premise in the filmmakers’ 2008 short, is basically about maternal love, in both its protective and possessive aspects. It opens with a prologue in which a stressed-out Wall Street financier (Nikolaj Coster-Waldau), having killed his partners and his estranged wife during the 2008 economic collapse, takes his daughters—three-year old Victoria and one-year old Lily—to an isolated, abandoned cottage in a remote, desolate forest. But when he’s about to kill Victoria too, he’s attacked by a tall spectral force with billowing gown and long, wispy hair.

Five years later, the financier’s brother Lucas (Coster-Waldau again) continues to fund search parties in the wilderness, and one comes upon the cabin—and the girls, both in a feral state and scampering about spider-like on all fours. Happily they quickly advance under the care of Dr. Dreyfuss (Daniel Kash), a psychologist deeply interested in the case. He’s also instrumental in securing custody of the girls for Lucas, a struggling artist, and his punkish girlfriend Annabel (Jessica Chastain), a guitarist, rather than their well-heeled, snooty aunt Jean (Jane Moffat), because they agree to keep the children in a nearby house so that he can continue to work with them.

But it quickly becomes apparent that the ghoulish figure who’d saved the girls from their father and kept them alive for half a decade in the forest has followed them. They call this apparition—seductive to them and threatening to anyone who might infringe on its relationship with them—“Mama,” and we’re eventually shown, in flashback, why it (or she, to be precise) is so obsessively attached to them. As it turns out, she’s mommie dearest to the nth power, desiring to keep the girls with her forever.

But Mama’s journey is juxtaposed with the development of the maternal instinct in Annabel, whom we initially see thankfully checking a negative at-home pregnancy test. As the story progresses, she quickly becomes the children’s sole caregiver after Lucas is hospitalized as the result of Mama’a intervention. At first Annabel’s brusque with the kids, but she gradually warms to them—especially Victoria, who slowly turns to her as well, infuriating Mama. Though Lucas shows up at the close to add a paternal note to the mix, he’s a distinctly secondary figure in a tale that’s definitely about the bonds between mothers and daughters and men are peripheral, and often obtuse, figures.

Unfortunately, the female characters aren’t drawn especially well. As written, Annabel is a fairly empty figure, and though Chastain tries admirably to fill out the content, the result is still pretty ordinary. The same might be said of little Megan Charpentier’s Victoria and Isabelle Nelisse’s Lily, though both are perfectly adequate, while Moffat makes an appropriately snooty Aunt Jean. In his double role Coster-Waldau is adequate but unimpressive, though he’s better in the prologue as the maddened father. Kash reminds one of a stern Tony Shalhoub as the unlikely psychologist.

In any event the most memorable personage in the film is Mama, “played” by Javier Botet with the assistance of an array of makeup artists and special effects people. She’s quite an impressive creation, though hardly an especially original one, and even the most ardent fan of horror pictures would have to admit that she’s overused—in such matters absence makes the spine tingle more than constant presence. Still, Mama is testimony to the picture’s technical proficiency, marked not only by Riestra’s camerawork, beautifully attuned to Muschietti’s measured pacing, but the entire physical production, including Anastasia Masario’s painterly design and Elis Lam’s supportive art direction. Mention should also be made of Fernando Velasquez’s score, which comes on too strong in the shock moments but elsewhere gives the film an appropriately “magical” backdrop.

All of that is in sync with the Muschiettis’ desire to fashion what amounts to a dark fairy tale, a sort of modern Brothers Grimm fable about the power—and danger—of motherly love. Unfortunately, the effect was actually greater in the three minutes of their short film than in the 109 that make up the feature. Quite simply, “Mama” merely draws out the premise rather than embellishing it with clever twists, and ends up feeling obvious and predictable as a result. It looks as gorgeous as the finest of del Toro’s own fantasy films, but lacks their richness and depth.