When Evil Lurks (2023) arrives with a premise so simple it sounds like a setup: two rural brothers discover a body near their farm and learn that a man in a nearby house is "rotten," possessed by a demonic entity on the verge of birth. What follows is not an exorcism film. It's an extinction event in slow motion, and writer-director Demián Rugna executes it with a coldness that makes most contemporary possession horror look decorative by comparison.
What the film does differently
The first and most important thing When Evil Lurks does is discard the rulebook. There's no priest arriving with holy water. No ritual that works. The film builds its own mythology, delivered in fragments through terrified locals: don't use firearms near a rotten person, don't bring them into a city, don't kill them carelessly, or the evil spreads. The brothers, Pedro (Ezequiel Rodríguez) and Jimi (Demián Salomón), learn these rules too late. They break almost all of them within the first act. The film's logic is strict and pitiless: ignorance is not mercy.
Rugna worked in Argentine genre cinema for over a decade before When Evil Lurks, and his control here is remarkable. He doesn't linger. Scenes cut before you've fully processed what you've seen, and the next one is worse. The rural setting, all muddy roads and tin-roofed houses in the Buenos Aires province, feels genuinely isolated, not in a postcard way but in a way that means no one is coming.
Violence as consequence, not spectacle
The film is extremely violent. This needs saying plainly because the nature of the violence matters: it's consequential, not theatrical. Each act of horror follows directly from a decision one of the characters made, often several scenes earlier. Rugna keeps a tight chain of causality running through the entire film. When children are put in danger, as they are here in scenes that will genuinely disturb a lot of viewers, it's because the plot has earned those stakes through consistent logic rather than reaching for shock.
This is where When Evil Lurks separates itself from the European extreme horror tradition. Films like Martyrs (2008) use extremity to chase a philosophical point about suffering. Rugna isn't interested in transcendence. He's interested in catastrophe: what happens when ordinary people make ordinary mistakes while carrying an extraordinary problem. The horror compounds. It doesn't redeem.
Rodríguez holds the centre
Ezequiel Rodríguez carries most of the film on a performance of escalating, internalised panic. Pedro isn't a hero. He's a man who keeps making the wrong call, usually the understandable one, and watching the consequences multiply. Rodríguez doesn't play for sympathy. He plays for truth. By the time the film's third act arrives, his face alone communicates the kind of cumulative exhaustion that most horror protagonists never reach.
The film also features a standout scene involving a woman who was once a "cleaner," a specialist in handling rotten cases. Her explanation of how the demonic entity spreads, delivered in a flat, bureaucratic tone, is one of the most effective pieces of world-building in recent horror. It treats the supernatural as a public health problem. The mundanity is the point.
Rugna's control of tone
Tone is where many possession films collapse. They start in dread, slide into melodrama, and resolve into a showdown between good and evil. When Evil Lurks never slides. The register stays fixed: bleak, matter-of-fact, and entirely without irony. There are no winking genre references, no comic relief, no character who exists to explain things cheerfully. The film treats its own logic with total seriousness and demands the same from the viewer.
It's worth comparing this approach to what Ari Aster does in Hereditary (2018): both films use grief and family fracture as the engine of their horror, and both refuse to offer comfort at the close. But where Aster's film builds toward ceremonial revelation, Rugna's film builds toward nothing except more loss. The ending is one of the bleakest in contemporary horror, and it earns that bleakness honestly.
A word on the mythology
The film's internal rules are consistent enough that horror writers could diagram them. The evil spreads through proximity, through bodily fluids, through sound. Guns accelerate it. The rotten person is not the threat: the birth of what's inside them is. Rugna deploys these rules across the film with the discipline of a screenwriter who knows that the scariest monster is one with clear, learnable, unbreakable mechanics.
This is the same quality that made The Wailing (2016) so devastating: a supernatural threat governed by rules the characters can almost grasp, but not quite fast enough. When Evil Lurks belongs in that company. It's not a film you enjoy. It's a film you survive, and then find yourself thinking about at 2 a.m. three weeks later.
Verdict
When Evil Lurks is one of the finest horror films to come out of Latin America and one of the most genuinely frightening films of the past decade. Demián Rugna has made a possession film that makes possession feel plausible, contagious, and final. It's available to stream via Shudder, where it sits exactly where it belongs: in the kind of library you browse at midnight, convincing yourself you're brave enough. You might not be. Watch it anyway.