Ezequiel Rodríguez in When Evil Lurks (Shudder/IFC Films)

Within the first 10 minutes of When Evil Lurks, you are witness to a decapitated body. A little later, a character hits herself repeatedly in the head with an ax. So, if you are looking for gore and shocking images, you have come to the right place. But what you also get in this deliciously creepy film is a growing sense of dread, some trenchant social commentary, a pitch-perfect tone, and fine acting.

The bloodbath all begins when brothers Pedro (Ezekiel Rodríguez) and Jimi (Demián Salomón) hear a gunshot outside their home in the Argentinian countryside. They head out to investigate and soon discover there is a “rotten” in the village. A rotten is someone possessed by a demon, and there are particular ways to dispose of one, but if you do it the wrong way, all hell literally breaks loose. The brothers try to alert the authorities, who seem to have little interest in interfering, which leaves Jimi and Pedro and a local hotheaded farmer, Ruiz (Luis Ziembrowski), to the task. Needless to say, they fail. The evil is unleashed, and the brothers race to save their families and stay one step ahead. However, their track record is not great.

Writer/director Demián Rugna has a masterful sense of control, parceling out information bit by bit, creating a world for his characters that is ordinary, save for the casualness that people talk about and deal with demonic possessions. His great gift is an ability to slowly ratchet up tension and dread by using all the tools available to him: creepy score, superb editing and camerawork, and committed actors. There are moments when you damn well know something is going to happen, even if you don’t know what it is, and Rugna bides his time, turning up the heat degree by degree until the tension is unbearable, and when he strikes, you are still surprised by the brutality. This guy is the real deal.

It takes a real talent to be able to cast someone who tells a story the moment you look at him. As Pedro, Ezekiel Rodriquez, rail thin, weary-eyed with a bushy grey beard, immediately brings you close to his character before he says a single word, or even moves. Jimi, a bit stockier with a ’70s pornstache and never without a cap on his head, always walks two steps behind and gives off a wariness and a will to protect his brother, who has apparently been through a lot, mostly due to awful life choices. Rugna takes the same amount of care with all his actors, from the loving mother who is clueless to her sons very, very pressing needs, and the rest of the family.

Rugna is surefootedness in his approach. He is supremely patient and trusts his story and his audience enough to unspool his bleak vision at the pace he desires. By the time of the climatic confrontation, you are bundle of nerves because you know at this point that Rugna has no hesitation to take risks. The fact that he doesn’t unspool a load of pyrotechnics or flashy editing but simply bears down on the story’s inevitable conclusion is admirable, and even more chilling.