Like the friendship at its heart, Cory Finley's superbly controlled rich-kid noir Thoroughbreds gets more complex and intense as it develops. The leads are a pair of posh Connecticut prep school teens, Lily (Split's Anya Taylor-Joy) and Amanda (Bates Motel's Olivia Cooke), one of whom feels too much while the other professes, convincingly, to feel nothing all. They will surprise themselves and each other as they discover that, between them, they have all it takes to plan and possibly execute a murder. They'll surprise audiences, too, as they each reveal themselves capable of decisions more terrible and tender than you might expect.
Posh, porcelain Lily wants to kill the stepdad (Paul Sparks) who rules over her palatial home. And since the guy's a vision of moneyed, muscled menace, you, of course, might be tempted to welcome this.
Thoroughbreds' best trick is to convince us, through the aching stillness of its stars' eyes, that it might not actually be a twisty, twisted noir inspired by the likes of Strangers on a Train. The film, much like teen lives, centers on performance: performance of self, performance of friendship, performance of the perfect life that we might believe at first Lily enjoys. When Lily suggests that they collaborate on the murder of her stepfather, it's hard to tell which of the girls is nudging the other -- and even, at first, whether they're even serious.
For all the fluid camerawork and exquisite exploitation of cinematic suspense technique, Finley is a playwright with a shrewd sense of act structure, of power dynamics, of revelations that prove as inevitable as they are shocking.