After their costly victory over President Krug and the Patriot Army, 18-year-old Kress and her Conspiracy travel to a newly medieval London, England where they are forced to fight their way through two warring factions amid a decimated hellscape. Their struggle for survival takes them on an epic quest through what’s left of London as they race to track down a pair of mythical twins, who are rumored to have the unique ability to enter the world of dreams.

In a secret facility called the Processor, Kress and her fellow Recruits are subjected to endless weapons training, violent puzzles, dangerous war games, deadly escape rooms, and impossible Virtual Reality simulations. In the end, they’ll get answers to questions they’ll wish they never asked.

In the year 2043, with the nation destroyed by war, 17-year-old Kress and her conspiracy of friends embark on a dangerous cross-country mission to locate and recruit other Emergents, the name given to teenagers who have begun to exhibit strange evolutionary abilities. Not all Emergents are ready to accept who and what they are, however, and some have even started using their abilities for selfish or evil ends. Now Kress has to figure out who is friend and who is foe as she risks everything to expose the government’s lies and take down the tyrannical President Krug once and for all.

In the realm of Kravan, children of lower-class citizens are raised in a prison-like structure called "The Tower" from birth until adulthood. Known as the Tethered, they are held in thrall until their powers reveal themselves around the time of their nineteenth birthday. Every year, the Tethered who are tested and deemed harmless are chosen to leave the Tower and join the outside world as servants to live in the households of the ruling class. Those who are deemed threats are taken away—and no one knows what happens to them, though they suspect the worst.

On her 17th birthday, Ashen Spencer is blindfolded and escorted to the massive, mysterious building known as the Arc to begin her year of training and testing in hopes that she can earn the Cure - a powerful drug given only to those deemed worthy to survive beyond their 18th birthday. Ashen has a chance to rise up from her former life of squalor and be granted a place in society, if the Panel - the mysterious group of powerful men and women in charge of the Arc - deems her year a success.