By all appearance, Emily (Phoebe Dynevor) and Luke (Alden Ehrenreich) are a couple cruising to a life of aggressively grabbed bliss. Freshly engaged, they’re intensely into each other and both feeling like they’re on the fast track at the hedge fund where they’re employed. There’s the little wrinkle that they’re keeping their relationship a secret of work, but that only seems to make their time together a little hotter. The real test arrives when Emily gets a major promotion that Luke believed was all his.

As written and directed by Chloe Domont, Fair Play is deliberately rough stuff. At the core, the film is interested in way a few blows to a fragile male ego can result in untold damage. Luke professes that’s he happy for his romantic partner’s success, but the smile looks strained from the start. Emily is now his boss, which is part of the problem. Domont shrewdly makes Luke’s spiral about far more than the altered power dynamic. His jealousy, manifested in more hues than a yard-long paint sample sheet, gradually leads to escalating toxic behavior. Ehrenreich plays the troubling progression with great care, avoiding both overt villainy and too much compensatory vulnerability. That subtlety is more compelling than a heel turn. Besides, anyone hoping for a more explosive portrayal never has to wait too long for a scene with Eddie Marsan as the head of the company, glowering like a pressure cooker inside a kiln ratcheted up to full blast, as is his custom.

Dynevor has the trickier role. Ehrenreich’s arced descent needs to be countered by Emily’s reaction to it and her navigation of new, demanding role simultaneously. Dynevor does well in both respects, but it’s clearly the two-hander moments with Ehrenreich that engage her the most. At every complicated stage of the characters’ shared journey, the two actors deliver a striking duet of intense feeling. Even when the plot starts depending on some fuzzy logic and questionable motivation to get to harsher turns that feel more like audience provocation than a plausible progression of the narrative, Dynevor and Ehrenreich remain convincing in their scenes together.

In her feature directorial debut, Domont impresses. Her talents as a writer and visual storyteller are evident, and she’s brave in sticking to her convictions. She clearly isn’t afraid of leading the audience to places of discomfort. When her instincts draw her into the dark, she doesn’t flinch. If Fair Play eventually runs too hot and breaks down, it’s hard to deny that Domont built a powerful engine.