In the utopian society of Xantera, nothing is a utopia beneath the surface. Twenty-three-year-old Saskia would do anything to tear down the Wall to liberate her people, but now it's too late. She failed to get the key. Failed to open the door. Failed to destroy the Guardians before she fell. But when Saskia finally comes face-to-face with the very Monster she's always been taught to fear, everything changes. Not only is life outside the Wall the opposite of all she's ever known, but a centuries-old force is at work, slowly waking up after years of dormancy. Together, Saskia and Lucan must face the truth that even the Guardians themselves could have never guessed—a truth that could save Xantera after all... Or destroy it.