Anya Taylor-Joy’s compellingly incongruent face is the best effect in the new thriller “Thoroughbreds.” Best known for playing the Puritan teen accused of practicing dark magic in the 2015 arthouse horror hit “The Witch,” the British actress has the eyes of a prim toddler and a full, sensual mouth somehow made up of sharp angles. Those mercurial features comprise a microcosm of writer-director Cory Finley’s debut: a cold, twisty mystery that keeps delivering surprises.
Imagine if the creepy twins from “The Shining” were separated at birth, adopted by upper-crust Connecticut families, became friends in school, had a falling out, were reunited by an SAT tutoring sesh, and decided to kill one of their stepdads instead. Unlike in ninth grade, the two girls aren’t exactly pals this time around — it’s hard to definitively say they even like one another — but they are allies and confidantes.
A long, close hug they share at the film’s start encapsulates their relationship: Lily (Taylor-Joy) in grudging discomfort; Amanda (Olivia Cooke, “Me and Earl and the Dying Girl”), recently diagnosed as an emotionless sociopath, with eyes deader than disco.
On break from boarding school, Lily agrees to tutor town pariah Amanda, an object of intense, horse-related gossip. In her crisp, office-ready blouses and with her preternaturally neutral demeanor toward her dickish stepfather Mark (Paul Sparks), Lily appears the very picture of the young American oligarchy learning how to settle into their perch atop society. But when Amanda suggests they kill Mark — or better yet, have him killed, while they enjoy an airtight alibi — Lily agrees in less time than it’d take a J. Crew order to arrive at her door.
It turns out good help is hard to find. In his last performance, Anton Yelchin plays a drug dealer with grandiose dreams and exclusively underage customers. Yelchin’s Tim is the most believable figure in this otherwise stylized drama, a pathetic, delusional lowlife who still deserves better than what’s coming to him.
The girls’ attempt to blackmail him into killing Mark is the first time we truly understand that they’re much more terrifying than we’d thought. It’s not insignificant that Tim’s family belongs to a much more modest income bracket than Lily’s or Amanda’s. But Finley declines to push the class angle here, which endows “Thoroughbreds” with a disappointing weightlessness.
Most of the action takes place in the mansion that Lily and Mark share with her widowed mother (Kaili Vernoff), and the patronizing, casually contemptuous way that Mark talks to his wife is genuinely gutting. But, intriguingly, Mark never says anything overtly abusive — a lack that contributes as much to the tension as the plunky, percussive, quasi-experimental soundtrack (by Erik Friedlander, “Oh Lucy!”) and the protracted, unsettling stares that Finley gets out of Taylor-Joy and Cooke. Needless to say, both actresses are fantastically affectless while suggesting a simmering wrath or a malign curiosity under the placidity.
Even with its measured pace and sparse plot, the film’s indulgence in stillness is one of the best things about it. An early scene in which Amanda eats cereal at her desk, looking blankly at the computer screen, is both alarmingly disquieting and profoundly relatable. (Is there anything more adolescent than killing time and being unhappy without having any idea what to do about it?)
As “Thoroughbreds” slithers toward its fitting yet convenient ending, it feels increasingly like we’re missing a key scene or two about Lily, especially when Mark gives her the talking-to she’s clearly been dreading. But if you don’t mind your movies nasty, brutish, and slight, you couldn’t ask for a more delectable chocolate-covered razor blade.