Some of the best horror movies veer off in unexpected directions. There’s nothing quite so nice as having absolutely no idea what’s going to happen next. And there’s nothing quite so dull as watching a supposedly scary movie line up the plot points and knock them down like dominoes.

But, really, there’s no point calling Penumbra’s unfolding mystery a horror movie. This Argentinian gem reminds me more of Martin Scorcese’s miniature urban odyssey, After Hours, with the same black humor and the same off-kilter sense of place. Penumbra’s main claim to being a horror movie is the prior body of work of the brothers who wrote and directed it, Adrian and Romiro Bogliano. Their last movie was Cold Sweat, a goofy potboiler about creepy old men who use social media to lure young people and then kill them with nitroglycerin. The kidnapped heroine is slathered in the volatile stuff, so she has to be rescued by slowly dragging her out of the building on a blanket so she won’t explode. But only after removing her clothes because, you know, they’re soaked in nitroglycerin. There hasn’t been a more perfect marriage of narrative and disrobing since Saffron Burrows stripped out of her wetsuit to electrocute a shark in Deep Blue Sea. The hero in Cold Sweat wears a shirt that says Sorcerer. Get it? If so, you’re exactly the kind of person who doesn’t deserve Cold Sweat.

Penumbra could easily get by with a nod to a couple of classic thrillers of the 70s. But if I told you what T-shirt the hero would wear, it would be a spoiler. The delight of Penumbra is having no idea where it’s going. That’s the point. It’s a smart, sexy, slow burn with a bit of subtle social commentary, a flawed and unlikable main character, a great sense of mystery, and a satisfying payoff.

Penumbra is currently available wherever fine videos on demand are sold. And for another example of why Argentina is a country worth watching for nifty genre movies, I also recommend the thoroughly charming Phase 7.