After defying the ruthless Enclave, surviving the wasteland, and upending the rigid matriarchy of Sylum, Gaia Stone now faces her biggest challenge ever. She must lead the people of Sylum back to the Enclave and persuade the Protectorat to grant them refuge from the wasteland. In Gaia's absence, the Enclave has grown more cruel, more desperate to experiment on mothers from out side the wall, and now the stakes of cooperating or rebelling have never...

In a future world baked dry by the sun and divided into those who live inside the wall and those who live outside it, sixteen-year-old midwife Gaia Stone is forced into a difficult choice when her parents are arrested and taken into the city.