A group of athletic, thrill-seeking women get together in the Appallachian Mountains to go exploring a cave. The year before one of them lost her husband and daughter in a horrendous car crash, so the others are somewhat worried about her. It's alluded to that the leader of the group-and the only American (the rest are British/Scottish), an Asian woman named Juno-was having an affair with that friend's husband, so things are uncomfortable between the two women.
At first the cave exploring goes well, until a small tunnel they crawled through collapses.
Now they must find another exit. The bad news is that this is an unexplored system of caves, not the caves they thought they were going to be in. Juno, who was in charge of the location, lied to them and thought it would be more exciting to go somwhere where no one has gone before.
But they are not alone. Living in the darkness are a type of human, the "Crawlers". They are albino, blind, have extremely good hearing and are adept at clinging to rock surfaces. They are also carnivorous and view the women as food.
This movie actually made me jolt in my seat a few times and I found it creepier than 2005's THE CAVE, which had a similar theme. In fact, I would say that THE DESCENT is one of the best horror movies of 2006.