In a world divided by gender allegiance, two young women navigate dangerous new terrain. The Gender Wars won't be fought with machines-they'll be fought with people. And when the women of West America wage war with men in the East, it'll be anything but unimaginative. In East America, the most fertile women go through excruciating body- and mind-altering training until their identities satisfy that of the State. They are the "Nancys"-white hair, light eyes, and no way to differentiate themselves from their identical "sisters." Nancy159 is fifteen. She's auditioning to be the seventh wife of President X, the ruler of the Eastern States. If she wins, she'll be married to the most powerful man in the world; if she loses, she'll die. Avis Baron is the daughter of the Luminary of West America. Recently, she stopped taking her Amplexus pill, taken by all women in W.A. to control their emotions. It turns out there's a lot she didn't know a person could feel-especially the way she's feeling about her friend Ethan. What is the source of a woman's power? Does it come from fertility, like the Nancys suggest? Does it come from brute strength and cold calculation, like the West believes? Or could it just be the simple beat of your own heartsong? The world continues to collapse and the Gender Wars loom on the horizon...XX v. XY.