Set 77 years after an atomic war has wrecked development, when a spaceship lodging humankind's solitary survivors sends 100 young detainees back to Earth, in a last endeavor to decide if it is habitable. They find that many endure the end of the world: the Grounders, who live in tribes secured a power battle; the Reapers, another gathering of Grounders who have been transformed into barbarians by the Mountain Men; and the Mountain Men, who live in Mount Weather, plunged from the individuals who bolted themselves away before the end times. Struggle for leadership, power struggle between Grounder clans, a rogue AI are going to be some of the problems awaiting them.