The morning after a violent thunderstorm, a thick unnatural mist rapidly spreads across the small town of Bridgton, Maine, reducing visibility to near-zero and concealing numerous species of bizarre creatures which viciously attack any human who ventures out into the open. The source of the fog and its inhabitants is never revealed, but strong allusions are made to an interdimensional rift caused by something known second-hand to the townsfolk as "The Arrowhead Project", long rumored to be conducted at a nearby top-secret military facility.