In a world divided by blood--those with common, Red blood serve the Silver-blooded elite, who are gifted with superhuman abilities--seventeen-year-old Mare, a Red, discovers she has an ability of her own. To cover up this impossibility, the king forces her to play the role of a lost Silver princess and betroths her to one of his own sons. But Mare risks everything and uses her new position to help the Scarlet Guard--a growing Red rebellion--even as...

As the struggle between the growing rebel army and the blood-segregated world escalates, Mare, who has the red blood of the common folk but also the silver ability to control lightning, must fight against the darkness that has grown in her soul.