PHOTO COURTESY IFC FILMS / SHUDDER

There are certain phrases used in reviews of horror movies — “not for the faint of heart,” “for hardened horror fans,” “unflinching,” “disturbing content” — meant to suggest that the casual viewer need not apply.

What we mean, when we use those phrases: Listen, this movie is messed up. (In more casual conversation, another word will replace “messed.”) 

All of these phrases, and more, can and should be applied to “When Evil Lurks,” a shocking and captivating tale of demonic possession in a small town.

For the many horror fans who found the recent “Exorcist” sequel to be a retread of the original, “When Evil Lurks” is a fresh take on demonic interference. In a remote Argentine village, two brothers discover the remains of a mysterious visitor in the woods. The trail leads to a small home containing a “rotten,” or a human possessed by a demon that would very much like to get out and wreak havoc.

As our characters attempt (very unsuccessfully) to rid themselves of their unholy problem and protect friends and family, they seamlessly drop some of the rules of this brand of possession: “rotten” individuals shouldn’t be killed by laypeople, mustn’t be addressed by name and can control the minds of nearby people and animals. As the quest grows more and more desperate, you’ll stop rooting for the evil to be defeated and begin simply hoping that anyone makes it out alive.

Directed by Demián Rugna, a rising star in the horror world, “When Evil Lurks” is not merely brutal in terms of its violence (though it assuredly is). It depicts a bleak, troubling world, where demonic possession is just one more obstacle thrown on the doorsteps of the underprivileged. You’re free to read any metaphor you like into it or just see it as sad commentary; life for many is nasty, brutish and short, and all three of those qualities can get much worse.

The story sags a bit in the back half, as the characters get into the weeds of demonology, and one location change too many complicates matters. There are scenes in the last half-hour or so that you’ll likely forget. They are balanced, however, by scenes earlier in the film that you will simply never get out of your mind. (Watch out for a very chaotic family reunion.)

Of course, all of those phrases at the top of this review serve as both a warning and an enticement. For viewers who are put off by shocking scenes and midnight-dark subject matter, “When Evil Lurks” will likely be several steps too far. For those stalwart genre fans looking to raise the bar, however, it will likely be a must-see.

My Rating: 7/10

“When Evil Lurks” is now playing at the Harris Theater. It will begin streaming on Shudder on Oct. 27.