Nona Grey arrives at the Convent of Sweet Mercy falsely accused of murder and guilty of something worse — a power so rare and dangerous that even the nuns who train assassins do not fully understand it. In a dying world where the ice advances and humanity clings to a narrow habitable band, the convent teaches its girls the arts of blade, fist, and shadow alongside ancient mystical gifts tied to long-vanished bloodlines. Nona must navigate a decade of training, fierce friendships, political conspiracies, and the wrath of the empire's most powerful figures.

Nona Grey is fierce, loyal, and morally complicated — a girl who has always been capable of great violence yet always chooses it in defense of those she loves. Her growth from a terrified child saved from the gallows to a holy sister with devastating power is the heart of the trilogy.

Across three books, Nona grows from a silent, traumatized child into a warrior-nun capable of reshaping the fate of her world. The series expands from the intimate world of the convent outward into imperial war, inquisitions, and a final confrontation with forces that have been shaping Nona's destiny since before she was born. Mark Lawrence weaves brutal action with deep emotional resonance and a love for the 'found-family' Nona builds among her fellow novices.