In the aftermath of the supervolcano's eruption in Yellowstone Park, North America is covered in ash. Farmlands cannot produce food. Machinery has been rendered useless. Cities are no longer habitable. And the climate across the globe grows colder every day.
Former police officer Colin Ferguson's family is spread across the United States, separated by the catastrophe, and struggling to survive as the nation attempts to recover and reestablish some measure of civilization . . .