Richard Young is looking forward to a quiet week with his wife and their little daughter. Firing up the barbecue should be the most stressful task he'll face. He has no idea of the hell that awaits him, the nightmare that will begin with an insistent pounding at his door. The stranger begging to be let in is being hunted. Not by a man or an animal, but by something that cannot be seen or heard, yet which has the power to crush and destroy anything in its path. It is a relentless, pounding force that has existed for centuries and has now been unleashed to terrify, to ravage...to kill.