There is no sun. There is no moon. There is only gray - the smog belched from coal-fueled factories. The Workers silently shuffle to their assigned posts. The Outcasts watch from the alley walls. On every corner, a Watcher stands stone-faced, a rifle in hand. This is the only life that exists. Beyond the mountains is a dream. But dreams are foolish in a place like this. Hannah has spent 19 years dodging Watchers and doing as she is told. When she wakes to the valley exploding in revolution, Hannah is forced onto a dangerous path, where nothing is what she believed.

After escaping execution, Hannah finds herself where she's always wanted to be...outside the valley of slaves. But the relief doesn't last, not when the rest of her people are still suffering. It's time to return. With the promise of help coming and the strength of new comrades, Hannah and Cash cross the mountains to rejoin the revolution. But winter has come, and the situation has only grown darker. The Outcasts are dying. The rebels are losing ground. With limited time, the rebel soldiers must hurry to try to convince more Watchers to renounce the Council's authority before the South arrives to take back their people.