On the afternoon of the spring Equinox, when the sun inexplicably vanishes from the sky, Ronnie Simpson becomes the most important person on the planet. A single mom and former pentathlete, Ronnie runs an experimental zeoponics farm (vegetation without sunlight) in Maryland, and the President of the United States believes that her expertise is crucial to the survival of the species.

As the earth’s temperature begins to drop rapidly at 2.5 degrees per hour, the President initiates an emergency plan to save a selected remnant of the human race within the “nuclear war” cave inside Mount Weather in western Virginia, but Ronnie refuses his direct presidential order to report to the cave, despite the involvement of her former lover, astrophysicist Zane Buchanan.

Will Ronnie go to Mount Weather before it’s too late?

What about her heart-damaged child?

What about the fate of the species?