In a futuristic society, Tally is about to turn sixteen, the age at which all teenagers have a mandatory operation to turn them into their world’s definition of “pretty.” Pretties live in a high-tech world of nothing but parties and fun, and Tally can’t wait to join it. But when Tally’s friend Shay runs away to live on the outside as an “ugly” instead of having the operation, Tally is forced by the authorities to find Shay and turn her in. When Tally eventually finds Shay with a band of rebels who are intent of revealing the more sinister aspects of the pretty society, Tally is forced to make a choice; either betray the rebellion (including her new love-interest) or give up what has been her dream for as long as she can remember.