The two central characters of “Thoroughbreds” look like all-American upper-class teenagers – except when you look closer to see their expressions, which range from oddly vacant to sullen.

Amanda and Lily are messed up.

The two central characters of “Thoroughbreds” look like all-American upper-class teenagers – except when you look closer to see their expressions, which range from oddly vacant to sullen. And they speak with the same strange emotional remoteness.

Former childhood friends living in upper-crust Connecticut, they are reunited when Lily (Anya Taylor-Joy of “The Witch,” “Morgan” and “Split”) starts tutoring Amanda (Olivia Cooke of TV’s “Bates Motel” and “Me and Earl and the Dying Girl”). Amanda has had some, well, issues, which is why she needs the help with schoolwork.

But soon the girls’ conversations turn to darker matters, and it becomes difficult to know if one is manipulating the other (and, if so, who’s doing what), or whether they’re manipulating each other, or whether they’re both genuinely about to embark on a deadly team effort.

That’s the fun of this lean, mean thriller from writer-director Cory Finley. This is Finley’s first film, and, boy, does he know how to keep moviegoers on edge and do it with style. With a spare soundtrack – a pulse-paced drum punctuated by occasional strings – his film builds suspense in a comically twisted way that leaves you guessing where it will all lead while you’re enjoying every minute of it.

Amanda doesn’t have feelings. No, that doesn’t mean she tries to suppress them. She really doesn’t feel emotions. Instead, to get by with other people, she feigns the signs that imply emotions. She smiles in the mirror – for practice. She has learned a technique to bring tears to her eyes. It’s all pretend, all a game to her.

Lily, in some ways, seems more “normal.” She hates her stepdad (Paul Sparks, memorable as the giggling mobster Mickey Doyle in HBO’s “Boardwalk Empire”), but could be the typical adolescent with a chip on her shoulder. Or maybe …

Really, the less you know the better. Taylor-Joy and Cooke are spellbinding, and Anton Yelchin, in his last role (he died in an accident at 27 in 2016), is just as good as the low-level drug dealer Lily and Amanda play with like two cats slapping around a mouse.

The film is gripping, and it doesn’t let up until the very end. But there’s more to the movie than just suspense. “Thoroughbreds” also provides a sly commentary on a modern society with shallow ideals of success and little regard for the value of emotions. “Empathy isn’t your strong suit,” one character says to another.

Meanwhile, the film asks whether a life without feelings is worth living. And it’s up to you to answer that question.