Yellowstone National Park sits on a hot spot: a plume of molten rock coming up from deep inside the earth capable of volcanic eruptions far greater than any that have occurred in times past. It has been silent for many years, providing false security for a nation unprepared for the full force and fury of nature unleashed.

Then explosions send lava and mud flowing far beyond Yellowstone toward populated areas. Clouds of ash drift across the country, nearly blanketing the land from coast to coast. The fall-out destroys crops and livestock, clogs machinery, and makes cities uninhabitable. Those who survive find themselves facing the dawn of a new ice age as temperatures plummet worldwide.

Colin Ferguson is a police lieutenant in a suburb of Los Angeles, where snow is falling for the first time in decades. He fears for his family, who are spread across America, refugees caught in an apocalyptic catastrophe in which humanity has no choice but to rise from the ashes and re-create the world...