The human revolution has risen against the Automae of Rabu, 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 they hadn't fallen in love first. Unbeknownst to Ayla, Crier escaped as well, joining with rebels and determined to find her way back to her love. When their paths finally cross and Ayla is charged to destroy the Iron Heart, neither girl is prepared for the secrets the mission will reveal.