Life quickly turns upside down in the small town of Ogden Marsh, Iowa. A toxin has been released in the town, and it is slowly turning the once peaceful residents into violent psychopaths. Sheriff David Dutton (Timothy Olyphant) and his wife Judy (Radha Mitchell) are two of only a handful of residents who have not been affected by this toxin. In an effort to preserve their safety and sanity, David and Judy band together with the few other sane townspeople left in an effort to save themselves, and hopefully, their town. Will this small minority of townspeople be able to find a way to stay safe and avoid the effects of the toxin, or will they also succumb to this mysterious toxin?