At fifteen, Nina Oberon leads a pretty normal life that includes family, friends, and school. However, Nina lives in a totalitarian future society in which all girls are required to get a Governing Council-ordered "XVI" wrist tattoo on their 16th birthdays, announcing to the world that they are ready for sex. Becoming a "sex-teen" is Nina's worst fear until, right before her birthday, her mother is brutally attacked and reveals a shocking truth to Nina with her dying breaths that changes everything Nina thought she knew about her life. Now, alone but for her younger sister, Nina must try to discover who she really is, all the while staying one step ahead of her mother's killer.