At the age of eighteen, Avery Whitewing is crowned High Priestess of Iden. And at the age of eighteen, Avery Whitewing becomes a fighter. In the world of Ois, three races of humans habituate the planet: the Avionaries, the Nocturnes, and the Walkers. Gifted with bird wings, Avionaries rule over Iden on Capitol Eden. The Nocturnes, gifted with bat wings, live in servitude to Avionaries. Lastly are the Walkers. Born without wings, they are forced into laboring down in the terra-sectors. When Avery is kidnapped the night of her birthday, her whole life takes a twisted turn. She discovers the world isn't as it seems. Taken in by Walkers, Avery becomes acquainted with the truth that those closest to her aren't what they claim to be, and the Walkers are everything she was told they weren't. Forced to face the reality of it all, Avery must make a choice for her country; for those with and without wings. With the help of a Walker, can Avery bring harmony to Iden or will the heavens fall?