As she approaches her 19th birthday, Nina discovers that she has been under a curse dating back to the era of Emperor Justinian in ancient Rome. This curse causes her to harbor a plague capable of annihilating humanity. According to the Book of Fire, Nina faces a critical decision: she can either continue living and risk infecting millions, or she can escape this fate by consigning herself to an eternity in purgatory. With only three days to make her choice, Nina is compelled to forge her own path.