Just before their sixteenth birthdays, when they will will be transformed into beauties whose only job is to have a great time, Tally's best friend runs away and Tally must find her and turn her in, or never become pretty at all.

After being captured and surgically transformed into a "special," teenaged Tally Youngblood, now a government agent programmed to protect society from outside threats, is ordered to eliminate the rebel colony New Smoke, Tally's former home.

In an alternate 1914 Europe, fifteen-year-old Austrian Prince Alek, on the run from the Clanker Powers who are attempting to take over the globe using mechanical machinery, forms an uneasy alliance with Deryn who, disguised as a boy to join the British Air Service, is learning to fly genetically engineered beasts. It is the cusp of World War I. The Austro-Hungarians and Germans have their Clankers, steam-driven iron machines loaded with guns and...