A sleepover attended by a gaggle of catty, over-privileged 12-year-old girls has deadly consequences in "#Horror," a bleak, imaginatively conceived 21st-century cautionary tale. Purported to be inspired by actual events, the film—the writing-directing debut of actor Tara Subkoff (2011's "Tanner Hall")—blends social-media-obsessed commerciality with cinematic avant-garde sensibilities. The results are wickedly oddball. Subkoff's efforts may be that of a novice making plenty of first-timer mistakes, but the overwrought, too frequently on-the-nose script is improved considerably by her unique and inspired auteur touch. With just one movie under her belt, she has already begun to carve an individualistic niche for herself. For all of its indulgence, there is nothing else quite like "#Horror" out there.

Looking to fit in with the popular, wealthier girls at her middle school, Sam (Sadie Seelert) attends a sleepover thrown by classmate Sofia Cox (Bridget McGarry). Sofia's hyper-modern Greenwich, CT, home—an architectural achievement she nonetheless complains is smaller than her last house—sits lonesomely atop a wooded hill, the spoiled inhabitants sharing space with offbeat experimental artwork, sculptures and video-installation units. When Cat (Haley Murphy) arrives for the slumber party, she appears to be dead-set on out-mean-girling her peers. After her bullying of overweight Georgie (Emma Adler) gets out of hand, Sofia sends Cat packing. What no one yet knows is a killer lurks in the snowy vicinity, having already savagely hacked up Sofia's philandering father (Balthazar Getty).

The hashtag-happy "#Horror" is a tongue-in-cheek reference to a competitive, rainbow-hued phone app the girls use where they post photos and rack up points based on the likes they receive. If these preteens use their smartphones irresponsibly, their lack of cyber decorum barely scratches the surface of the hurt they are capable of causing. Director Tara Subkoff doesn't sugarcoat the ruthlessness of her barely adolescent characters, observing their concerning unsupervised antics as a possible murderer spies on them from outside and Sofia's unhappy mother, Alex (Chloë Sevigny), heads to an AA meeting with a glass of vodka on the rocks in hand.

"#Horror" is an intriguing hybrid evoking teen slice-of-life dramas and slice-and-dice slashers. On paper, it may seem decidedly cut-and-dry, but it is in the little visual details where the film transcends its familiarity. The production design by Daniel Subkoff and Tara Subkoff is an unsettling triumph, with a table of nightmarish masks, a pulsating egg yoke mounted on the wall, a bloody nude statue whose eyes open and close, and a black-and-white photo of sack-headed goblins in the living room eerily personifying the inanimate surroundings. A seemingly alive house of horrors with a very real psychopath prowling the property, this invaluable location helps to lessen the creeping monotony of its characters' petty ways. Classing the proceedings up further is the participation of Chloë Sevigny (2010's "Barry Munday"), bringing welcome layers and a perfectly ridiculous origami scarf to the role of Sofia's floundering mother. By contrast, Timothy Hutton (2010's "The Ghost Writer") overacts to a downright hammy degree as Cat's unstable father, Dr. Michael White. "#Horror" is something of a hodgepodge of spare parts, yet immensely interesting all the same. There is a method to Tara Subkoff's directorial madness, and what she has put to film is nothing if not bizarrely, indelibly auspicious.