In a solar system where The Authority decides who lives and who dies, only one of their own executioners can stop them. Glade Io is a trained killer. Marked at a young age as an individual with violent tendencies, she was taken from her family and groomed to be a Datapoint - a biotech-enabled analyst who carries out the Culling. She is designed to identify and destroy any potential humans that threaten the colonies: those marked as lawbreakers, unproductive or sick. But when she's kidnapped by rogue colonists known as the Ferrymen, everything Glade thinks she knows about the colonies, and The Authority that runs them, collapses into doubt. Pulled between two opposing sides, and with her family's lives hanging in the balance, Glade is unsure of who to trust - and time is running out.