A gruesome and psychological exploration of the greatest fear of all: the unknown. 16-year-old Sam awakens at home, all alone, immersed in the dark, to the sounds of distant chaos outside. In the midst of figuring out what's happening, his older brother, Mike, suddenly returns home to take him to safety, but both are forced to retreat to their claustrophobic basement. There, together they learn to confront their own fears, trapped with the mysterious, yet inevitable doom.