Four hundred years after a nuclear apocalypse, all humans are born in pairs: the Alphas, and their deformed Omega twins, who are ruthlessly oppressed. But despite their claims of superiority, the Alphas cannot escape one harsh fact: Whenever one twin dies, so does the other.

Following the events of The Fire Sermon, the Omega resistance has been brutally attacked, its members dead or in hiding. The Alpha Council's plan for permanently containing the Omegas has begun. But all is not entirely lost: the Council's seer, the Confessor, is dead, killed by her twin's sacrifice.

Cass is left haunted by visions of the past, while her brother Zach's cruelty and obsession push her to the edge and threaten to destroy everything she hopes for. As the country moves closer to all-out civil war, Cass will learn that to change the future she will need to uncover the past. But nothing can prepare her for what she discovers: a deeply buried secret that raises the stakes higher than ever before.