The Kola Superdeep Borehole is the largest Russian drilling project in the world, attempting to drill as far as possible into the Earth’s crust. After reaching depths of nearly seven miles below the surface, unexplained sounds resembling the screams and moans of numerous people were reported and the borehole was shut down. But when a small team of scientists and military personnel set out to unearth the source of the strange sounds, they end up discovering the greatest threat that humanity has ever faced.