Going in, you don't want to know too much about the pulverizing, nerve-frying shocks that Brit writer and director Neil Marshall is merciless about unleashing in The Descent. But know this: Unlike Marshall's Dog Soldiers, which focused on guys under pressure, The Descent is all about women facing the freak side of Mother Nature and themselves. Led, or in this case misled, by know-it-all Juno (Natalie Mendoza), the spelunking sextet decides to go caving in Appalachia, a sport unsuited to the weak of heart. Sarah (the excellent Shauna Macdonald) qualifies in that department, having suffered a family tragedy a year before, leaving her with lingering resentments about Juno.
That's the setup. Marshall takes his time at first, letting us watch the dynamic among the women, who all have issues with one another that aren't expressed on the surface. Once lost inside the cave — and they're lost big-time — violence manifests itself in the form of blind, milky-skinned, male predators who attack them out of nowhere with bone-crunching zeal. Are they inbred mutants or the longtime grudges among the women made creepy flesh? Until an overwrought finish out of Carrie, Marshall keeps you guessing with nightmare-making skill. Prepare to be scared senseless, and then, when you think you have it figured, your certainty will be shaken by scenes built to scare you even more.