Centuries after nuclear war destroyed our planet, humanity struggles to rebuild. It’s been a month since the dropships landed and the Colonists joined the Hundred on the ground. The teens, once branded juvenile delinquents, are now leaders among their people.

The Colonists and the Earthborns are celebrating their first holiday together when, to everyone’s horror, they’re attacked by a group of strangers whose unusual battle cries fill the air. The newcomers kill scores of people, seize prisoners, and pillage crucial supplies. When hotheaded Bellamy and his analytical girlfriend Clarke discover that Wells, Octavia and Glass have been captured, they vow to get them back at all costs. But as they go after their new enemies, Bellamy and Clarke find themselves increasingly at odds, unable to agree on a plan to save their friends.

Meanwhile, Wells, Octavia, and Glass are being slowly brainwashed by their captors, religious fanatics with one goal: to grow their ranks and “heal” the war-ravaged planet… by eliminating everyone else on it.