It has been seventeen years since the event that killed most of the people on the planet. The violence that swept the country for so long is gone, and Ben and Lila are now living a peaceful existence in their Yellowstone community. But more trouble is looming, and when their daughter Katie--now sixteen and going by the name of Cat--and eleven other teenagers leave to explore the country, that trouble hits home.

When two of the teens, one near death and the other deep in shock, return to Yellowstone a month later with the story that one member of the group is dead and the rest have scattered after a vicious attack by a new enemy, Ben and Lila know they must go after their daughter and her friends.

But where? And are they too late?