It’s a reoccuring gambit in many a thoughtful horror film to emphasize not only the external, but the internal. Humanity, after all, can be deadly; it’s a dangerous idea that dates back to Night of the Living Dead, and that terrifying final shot of the lone survivor’s fate at the hands of man.

It’s also a terrific premise to create true horror; after all, how do we truly make something horrifying when our protagonists are cornered by the supernatural? Take Danny Boyle’s excellent 28 Days Later: sure, the zombies cripple us with fear, but it becomes truly unsettling when all the chips our down and our heroes have to seek solace with some shady individuals. The compound they arrive at may be safe from zombies, but no matter; they also have to survive a series of lusty, alpha-male soldiers. Isn’t it somehow more terrifying when even your safe place isn’t safe?

Neil Marshall’s savvy, claustrophobic The Descent sends a group of lithe, athletic spelunkers into an uncharted cavern, and lets the darkness swallow them whole. He takes three well-traveled horror ideas and cleverly weaves them into something spectacularly scary: 1.) The primal fear of being trapped, 2.) The paranoid fear of not knowing who you can trust, and 3.) The less-realistic but nevertheless potent fear of being eaten alive by cave-dwelling subterranean monsters.

It’s a simple concept: traumatized heroine Sarah (Shauna MacDonald) and the adventurous, outdoorsy Juno (Natalie Mendoza) lead a group of their friends into an undiscovered cavern. There, they discover that a.) there may not be a conceivable way out, and b.) indigenous, carnivorous critters might just want to eat their flesh. This sets the stage for a spectacularly freaky adventure; Marshall, the director of chintzy-but-effective genre throwback Dog Soldiers, knows his way around this cave, and knows what danger lurks around every corner. The creatures, resembling an inbred, violent Gollum, materialize in backgrounds, scurry past our heroines just out of frame, and lurk until it’s time to strike. Tension is dealt out minimally, only coming to a boil when the film’s narrative is at its breaking point; like the 2006 remake of The Hills Have Eyes, it’s a film as much about our protagonist’s blood baptism, one that slowly unravels the processes and extenuating circumstances that create a cold-blooded killer.

It’s also about the horrors of the natural world; bones are broken, excruciating climbs are mounted and botched, and that’s scary too. But what makes The Descent a horror movie and not an adventure thriller is its aesthetic — dark, grimy, shadowy, drenched in rivers of blood. It’s also one of the most fatalistic horror movies ever created: it’s a film that begs to be seen with its original ending intact, instead of the cropped happy ending spoon-fed American audiences. The Descent is pure scares, nothing more — it’s a film that catches in your throat and stops your heart.

Extra Credit: For more of the pure, visceral terrors of being trapped, look no further than Adam Green’s nightmarish Frozen. The scares are real — no flesh-eating monster men here — but as the darkness closes in on three coeds trapped on a ski lift, and the wolves start to circle below, it boasts the same increasingly hopeless, noose-tightening feel.

More 31 Days of Halloween:
Day 1: May
Day 2: The Night of the Hunter