In the aftermath of a global solar flare that has decimated the human population and wreaked havoc on Earth, Dr. Riley Poole embarks on a treacherous 1,500-mile journey to learn the fate of her two youngest children.
After making the heart-wrenching decision to leave her injured daughter, Julia, in Virginia, Riley and her new husband, Coop, strike out into the wilderness toward Colorado. Along the way, they cross paths with old acquaintances and combine resources to travel together. Riley and Coop soon get life-altering news and learn that one member of their group has put them in grave danger, forcing them to stay one step ahead of a hostile, rogue government. 
Will Riley have the wit and courage to survive the journey and reunite her family?