Two sisters have always stood together. Now, they're the only ones left. In the shadow of Mount Hood, sixteen-year-old Tennant is checking rabbit traps with her eight-year-old sister, Sophie, when the girls are suddenly overcome by a strange vibration rising out of the forest, building in intensity until it sounds like a deafening crescendo of screams. From out of nowhere, their father sweeps them up and drops them through a trapdoor into a storm cellar. But the sound only gets worse ...