Five hundred years in the future, earth is no longer populated by humans. The new guardians of Earth, the genetically engineered Erta, have reversed climate change. They are now faced with a dilemma; if they reintroduce the rebellious and violent Homo sapiens, all of their work will be undone. They decide to raise one final child, a sole human to help decide if humanity should again inherit the Earth. But the quiet and clinical Ima finds that there is more to raising a human than she had expected and that there is more to humanity's history than she has been told.

Less than 60 kids awaken on a distant planet. The colony ship they arrived on is aflame. The rest of their contingent is dead. They've only received half their training, and they are being asked to conquer an entire planet. Before they can, however, they must first survive each other.

Officer Ren Hopper is an enforcement ranger with the National Park Service, tasked with duties both mundane and thrilling: Breaking up fights at campgrounds, saving clueless tourists from moose attacks, and attempting to broker an uneasy peace between the wealthy vacationers who tromp through the park with cameras, and the residents of hardscrabble Cooke City who want to carve out a meaningful living. When Ren, hiking through the backcountry on his day off, encounters a tall man with a dog and a gun chasing a small black bear up a hill, his hackles are raised.

Shana wakes up one morning to discover her little sister in the grip of a strange malady. She appears to be sleepwalking. She cannot talk and cannot be woken up. And she is heading with inexorable determination to a destination that only she knows. But Shana and her sister are not alone. Soon, they are joined by a flock of sleepwalkers from across America, on the same mysterious journey. And like Shana, there are other "shepherds" who follow the flock to protect their friends and family on the long dark road ahead.

In an unspecified future, the United States' borders have receded behind a salt line - a ring of scorched earth that protects its citizens from deadly disease-carrying ticks. Those within the zone live safe, if limited, lives in a society controlled by a common fear. Few have any reason to venture out of zone, except for the adrenaline junkies who pay a fortune to tour what's left of nature. Those among the latest expedition include a pop star and his girlfriend, Edie; the tech giant Wes; and Marta, a seemingly simple housewife.