Producers: Nima Yousefi, Mika Ritalahti and Nico Ritalahti   Director: Hanna Bergholm   Screenplay:  Ilja Rautsi   Cast: Siiri Solalinna, Sophia Heikkilä, Jani Volanen, Oiva Ollila, Reino Nordin, Ida Määttänen and Saija Lentonen   Distributor: IFC Midnight

Grade: B-

Horrors movies about split personalities go back at least to “Dr. Jekyll and Mr. Hyde” and “The Wolfman,” and there have been some intriguing more recent examples like “The Other” and “Goodnight Mommy,” and even—depending on your reading of them—“The Hitcher” (the original, not the dreary remake) and “Gerry,” to mention just a few.  Hanna Bergholm’s debut feature is in that tradition, and upholds it quite nicely.  But it also takes satirical aim at overbearing parenting and would-be internet celebrity, while turning “E.T.” on its head.  It may try to be entirely too many things for comfort, but if not a complete success, it proves a fascinating jumble.

In an extraordinary debut, Tinja (Siiri Solalinna) is a twelve-year old living with her father (Jani Volanen), mother (Sophia Heikkilä) and younger brother Mathias (Oiva Ollila).  The dominant figure in the household is mother, an almost insanely energetic woman who presents the family as living in a bubble of perfect contentment and joy in a blog called “Lovely Everyday Life” she films herself and posts online. (Production designer Päivi Kettunen gives their house a bright pastel look that cinematographer Jarkko T. Laine shoots in bright colors until shadows intrude.)  Her milquetoast husband acts the part of the happy, supportive dad, and little Mathias, actually a pretty obnoxious kid, squirms in the part of the smiling tyke but goes along.

A major aspect of the picture-perfect family portrait Mom is anxious to present to the world is the gymnastic expertise of Tinja, whom she pushes to practice to the limit in preparation for an upcoming competition.  Her daughter is a vehicle for her own unrealized ambitions, it’s suggested, and though she’s not happy in the role, she glumly submits to her mother’s pressure.  It becomes more stressful, however, when Reetta (Ida Määttänen), a girl who’s a better gymnast, moves in next door and immediately becomes Tinja’s main competition in gymnastics class, their coach (Saija Lentonen), quickly assessing her superiority.

Three things happen that alter Tinja’s life to an incredible degree.  Reetta’s dog nips at her during their first encounter.  Tinja walks in on her mother in an affectionate embrace with handsome handyman Tero (Reino Nordin), which she’s asked by mom to hold as a secret between them.  And when a black bird crashes into the living room window and rampages around the place, Tinja catches it in a rug and is about to turn it loose outside when her mother grabs it and breaks its neck, telling her daughter to toss it into the garbage.

But that’s not the end of the avian intrusion.  Tinja finds that the dead bird has disappeared, and then is awoken during the night.  Venturing out into the dark woods, she discovers the bird guarding an egg that the girl takes back to her bedroom and nests in a stuffed toy.  The egg grows and eventually hatches, releasing a creature that looks something like a huge winged mantis.  Tinja bonds with the thing, which she names Alli and hides from the rest of the family.

The hatching is but the start of Alli’s transformation as the creature gradually takes on the appearance of Tinja’s double.  It/she also reciprocates the girl’s darkest desires, becoming in effect as much the active expression of her id as Hyde was of Jekyll’s or the Krell-created monster was Morbius’ in “Forbidden Planet”—especially after Tinja goes to Tero’s house and finds out not only the depth of his relationship with her mother, but how her mother’s attentions are even more divided than she’d realized.  Alli’s targets escalate to include everyone who appears to Tinja to be an antagonist, a rival or merely a disappointment.

There’s no shortage of tension and violence in “Hatching”—with imagery, crafted by creature designer Petteri Mäkinen, SFX makeup supervisor Conor O’Sullivan, and creature and visual effects supervisors  Gustav Hoegen and Bert Deruyck that’s genuinely unsettling, especially as shot by Laine.  But it’s set against Kettungen’s bright, ostensibly cheery production design and Ulrika Sjölin’s attractive costumes.  Linda Jildmalm’s editing, alternating between smooth and jittery, adds to the sense of dislocation, as does Stein Berge Svendsen’s eerily pretty score.

Newcomer Solalinna anchors the film with a creepily convincing portrait of a quiet, recessive girl whose emotional suppression proves untenable.  But the other performances are no less notable, particularly that of Heikkilä as a manic woman so centered on herself that she seems to have no inkling of—or care for—the damage she’s doing to others.  Volanen is perfect as a squishy fellow who’d prefer to remain oblivious of unpleasantries, while little Ollila makes pudgy, bespectacled Mathias so unlikable that you might want to see him added to Alli’s list of victims.  Against this quartet—or perhaps quintet—of specimens Nordin comes across as agreeably normal.

“Hatching” is an assured, unnerving horror film of the elevated sort, one that adds some satirical punch to its genre foundations.