The Blood-Red Night of Hatchet Valley

Hatchet Valley is a deep rocky cleft in the earth, where people live if they're too mean or too weird for anywhere else. Other folks go there if they need or want to be away from ordinary life, or simply campers. Between these rocky walls drops a catalyst one morning, a peculiar artifact from somewhere else, and within an hour, Hatchet Valley becomes the most dangerous place on Earth, filling up with creatures that are no longer people, no longer animals, but they are voracious, fast, and smart.
But if there's one thing that could possibly unite a group of misfit strangers, it might just be such a threat. By dawn, the final confrontation between the remaining survivors of Hatchet Valley and the gray shaggy wave of teeth that hunt them will decide not just the fate of that Valley, but perhaps the entire planet.