For Cressida Quillionette, Cinderbloom Academy is everything she could never have if she remained in her home town. It is a gateway into a world of possibilities, but attending the secluded academy means she can never go back home. She has to make it count. After her years at the lower school, she is finally admitted to the Head School, and she is even paired as roommates with her best friends, including Miles, the boy with whom she's been testing a romantic relationship. And when she gets her class list, she discovers that this small-town clockmaker's daughter is to be transformed into a genteel young sorcerer. But students are forbidden to discuss classes with one another, and the strictures of the school begin to cut her off from her friends. Miles suffers mysterious injuries he won't talk about. Cressida has told herself until now that the rules and secrecy are all for the best, but there are signs of something dark beneath the surface-too many signs. When the enigmatic Headmaster pulls her aside for specialized instruction, she is submitted to an experimental ritual that changes her indelibly. Now she finds herself cornered by the question: what exactly is the change the Headmaster wishes his students to effect on the world? Is losing her humanity worth it? And when the time comes to fight back with her fellow students, will she?