It’s amazing how careful characterization can elevate a simple horror movie. You don’t get much simpler than the premise of The Descent, in which a group of women friends explore a cave and run into … you don’t want to know. What makes this work is writer-director Neil Marshall’s grounding of the fantastical terrors in real-world fears. The movie opens with an accident that tears apart the life of one of the cavers (Shauna Macdonald), then jumps a year ahead to the expedition. Add tension, suspicion and hints of betrayal that simmer among the women once things start to go bad and The Descent taps into the heightened hysteria that made The Blair Witch Project so unnerving.