For too long, Automae have lorded over the kingdom of Rabu, oppressing its human citizens. But the human revolution has risen, and at its heart is Ayla. Once a handmaiden, now a fugitive, Ayla narrowly escaped the palace of Lady Crier, the girl she would've killed if she hadn't fallen in love first. Now Ayla has pledged her allegiance to Queen Junn, who can help accomplish the human rebellion's ultimate goal: destroy the Iron Heart. Without its power, the Automae will be weakened to the point of extinction. Ayla wants to succeed, but can't shake the strong feelings she's developed for Crier. And unbeknownst to her, Crier has also fled the palace, taking up among traveling rebels, determined to find and protect Ayla. Even as their paths collide, nothing can prepare them for the dark secret underlying the Iron Heart.