The fourth book in the New York Times bestselling series The 100 finds the teens facing down a new threat—a cult that wants to take out everyone in their path in order to save the planet. Inspiration for the celebrated CW show.

It's been a month since the new dropships landed and the rest of the Colonists joined the hundred on the ground. The teens, once branded juvenile delinquents, are now leaders among their people. It should be a time for celebration and togetherness, but a new threat appears before long: a fanatical cult determined to grow its ranks and 'heal' the war-ravaged planet ... by eliminating everyone else on it.

After scores of their friends are captured, Clarke sets off to retrieve them, certain that she can come to an understanding with these strangers. Bellamy has a different plan; he won't let anything—or anyone—get in the way of saving the people he loves. Meanwhile, in captivity and scared for their lives, Glass falls under the spell of the cult's magnetic message, and Wells has to learn how to lead again. Unless the rescue party arrives soon, the teen captives will face a fate more terrifying than anything they could imagine.

If the Hundred ever want to call this dangerous planet home, they'll need to put aside their differences and fight to protect themselves and their world.