Ruby never asked for the abilities that almost cost her her life. Now she must call upon them on a daily basis, leading dangerous missions to bring down a corrupt government and breaking into the minds of her enemies. Other kids in the Children's League call Ruby "Leader", but she knows what she really is: a monster.

When Ruby is entrusted with an explosive secret, she must embark on her most dangerous mission yet: leaving the Children's League behind. Crucial information about the disease that killed most of America's children-and turned Ruby and the others who lived into feared and hated outcasts-has survived every attempt to destroy it. But the truth is only saved in one place: a flashdrive in the hands of Liam Stewart, the boy Ruby once believed was her future-and who now wouldn't recognize her.

As Ruby sets out across a desperate, lawless country to find Liam-and answers about the catastrophe that has ripped both her life and America apart-she is torn between old friends and the promise she made to serve the League. Ruby will do anything to protect the people she loves. But what if winning the war means losing herself?