Some horror films function as a dare. In When Evil Lurks, the challenge isn't just whether or not you can handle the scares in this possession tale, but if you can stomach its unrelenting brutality.

Horror connoisseurs should expect no less from writer/director Demián Rugna, the twisted mind behind the harrowing 2017 film Terrified. But for those who might haplessly wander into this story of demons ripping apart a family — sometimes literally — the terrors within may be more than shocking. They may be the kind of haunting that follows you home, howling in your ear as you try to fall asleep.

For some of you, that might be enough to put When Evil Lurks on a never-watch list, while others may be already psyching themselves up to see if they can handle this gory provocation of a film.

What is When Evil Lurks about?

Credit: Shudder

Our story begins in a remote village, where brothers Pedro (Ezequiel Rodriguez) and Jimmy (Demián Salomón) live in a humble cabin. What has led them here? That is not immediately clear or even important. After all, there are gunshots in the night. Though they've got guns of their own, the brothers know it’s best not to wander out into all that murky black, where anything might lurk. What they find the next morning is a scene of gruesome violence but few answers.

Well-meaning and willfully naïve, they visit their neighbors, seeking to understand what they’ve seen in the woods. What they find is a young man transformed by evil. His body is bloated to the point of looking like a human worm, distended and covered in boils and pus. His family is in desperation for what to do next, but the answer is never simple.

SEE ALSO: Exclusive 'When Evil Lurks' clip teases mind-splitting terror

What follows are the brothers' attempts to rid their town of evil, and failing that, to flee from it. But from those first gunshots in the woods, you should know this is not a story with a happy ending.

When Evil Lurks will make even the most hardened horror fans gag.

Credit: Shudder

Do not watch this film while eating. I made the mistake of trying to watch When Evil Lurks over lunch. As soon as the brothers come into view of that possessed body, I realized mistakes had been made. When Evil Lurks is fecund with gross visuals so masterfully made that you can practically smell the rancid odor of a body rotting from the inside out. Close-ups of soiled flesh are far more unnerving than some slick jump scare. There's a reason they refer to the possessed as "the rotten." But this bloated distortion of the human form is just the beginning.

Your stomach may flip in this early sequence, but as Pedro aims to save his children from this contagion of evil, those who are faint of heart may well pass out. It's not just the innocent who won't be saved from the savage violence of the rotten. It's that this director will not blink in showing us exactly what that carnage looks like.

SEE ALSO: 'When Evil Lurks' disturbing ending, explained

When Evil Lurks is a horror story of how parents fail.

Credit: Shudder

Peppered with breathtakingly horrid bits, this film could easily be written off as a cynical challenge, trotting out well-meaning men and their adorable children, only to dash our hopes of their salvation like a kid's head might be dashed on the flagstones. Unlike the ghoulish kills of Saw movies, the violence here is captured resolutely, without leering. There's no sense that we are meant to be darkly delighted by the violence, but more in genuine shock and awe of how thoroughly this contagion of evil spreads from neighbor to landlord to pregnant wife and beyond. But there's a method in this madness.

Midway through the film, we not only learn that Pedro has children but also why he is not living with him. Before this movie even started, he had already failed them, having been kicked out of their lives by their protective mother. Now he's barging back into their home, determined to do right this time. And the mistakes he makes along the way are horrific but also all too human.

As the brothers bumble — first for a solution, then for escape — we are drawn into their plight, even as we feel the inescapable weight of it. In this way, When Evil Lurks is a uniquely dreadful cinematic experience that forces you to understand the extreme terror of being a parent who cannot control the world that surrounds their soft, sweet, and woefully unsafe children.

If this Halloween season, you're looking for a new movie that is not only scary but will fuck you up, you can't do better than When Evil Lurks.

How to watch: When Evil Lurks opens in theaters Oct. 6 and premieres on Shudder Oct. 27.