The Gearbreakers struck a devastating blow against Godolia on Heavensday, but the cost of victory has been steep. The few rebels who've managed to escape the empire's retribution have fled, hunted by Godolia's only surviving Zenith. Eris has been held prisoner since the attack on the capital city that almost killed her. And she begins to wish it had when she discovers Sona—the girl she would tear down cities for—also survived, only to be corrupted by the Zenith. The cybernetic brainwashing that Sona has undergone now has her believing herself a loyal soldier for Godolia, and Eris' mortal enemy. With the rebellion shattered, the Gearbreakers' last hope for victory will depend on whether Eris and Sona can find their way back to each other from opposite sides of a war . . .