The unseen has always been the filmmaker’s best friend and darkness one of their greatest tools. It was something Val Lewton understood when he took over RKO’s B-horror unit. In a decade when Saw and its ilk was showing us more than we cared to see, writer-director Neil Marshall turned the lights down. Six women spend an annual holiday spelunking in the Appalachians. Alas, this day they’ve picked the wrong tunnel to wriggle down. Flashlights and torches reveal bleached bones. Soon the women are being picked off one-by-one by barely glimpsed mutants. Marshall has studied horror and understands it. He knows the women have to be more interesting—and possibly more savage—than the mutants, and they are. He understands that horror–as opposed to say, the western–is a specifically feminine genre. The final girl emerges from the cave reborn, but the past is still determined to have its way with her. Shocking and grimy, The Descent won’t be scrubbed off.