Ashlee is terrified of birds. Everybody in the Citadel is. Birds are blamed for the Plague that destroyed most of their civilisation.
Guards now patrol the city to keep it free of birds and other dangers such as the Outsiders who live free in the wilds, and the Egghead scientists who challenge the truth of their stories, and ideas that lie in books and technologies.
Ashlee is a slave to her wicked stepfamily, but when a yellowhammer comes tapping at her window, it leads her to a message of hope ... and her lost brother.