Twenty-year-old Liana Castell must be careful what she thinks. Her life is defined by the number on her wristband -- a rating out of ten awarded based on her usefulness and loyalty to the Tower, and monitored by a device in her skull. A device that reports forbidden thoughts. Liana is currently a four, the lowest possible acceptable score. When her worst nightmare comes to pass and she drops to a three, desperation spurs her down a path few dare to tread.