When a mysterious toxin transforms the residents of a small town into murderous maniacs, Sheriff Dutton (Timothy Olyphant) and a small band of survivors must fight for their sanity and their lives amidst a mandated government quarantine. Now, Dutton, his pregnant wife Judy, his deputy Russell and frightened medical-center assistant Becca work to discover the source of this scourge while fending off their infected friends and neighbors.