Sam Phoenix (Marsters) is an honorable yet guilt-ridden outlaw who arrives in a small Old West town to be executed for his various crimes. But his execution is interrupted by the unexpected invasion of giant uranium-based bugs, forcing Sam and a small band of survivors to take refuge in a church. As the voracious bugs fall onto Earth to feed and terrorize the town’s citizens, Sam finds himself the reluctant leader of a small group of townsfolk.