People need to be monitored, or they'll repeat the mistakes of the Desolation, a centuries-old war that killed billions of people and destroyed civilization. Skye is part of the Society, the hi-tech, nanite-endowed group responsible for making sure that the millions of surviving people—grubbers—are confined to the ancient, decaying cities where they can be watched to ensure they aren't redeveloping the weapons technology that came so close to extinguishing life on the planet. When the Society's monitoring programs pick up troubling developments in one of the grubber cities, Skye is ordered in to deal with the man responsible, but what—and who—she finds once she arrives will change everything.

They armored Skye's body and taught her how to kill, but didn't do anything to shield her heart. They injected her with nanites to make her faster and stronger, but that didn't make her ready to meet Brennan. She arrived expecting to find a despot—heir to a failed system of thinking—and instead found a visionary intent on rebuilding the world. Now, with Skye's masters poised to destroy Brennan's city, she will be forced to turn her skills against the very people who trained her. Only she can save the man she loves and the dream he's trying to realize, but doing so may very well destroy her.

Faced with helping to murder hundreds of thousands of innocents—including Brennan, the rebel leader she's grown to love—Skye did the only thing she could. She defected and fought her way through the Society's troops, bringing along all of the people who meant the most to her. Armed with a captured Society dropship and the advantage of surprise, Skye and Brennan finally have a chance to make a future for themselves but first they are going to have to fight their way past the Society's single most dangerous asset, and this time even Skye might not be able to guarantee their success.

Falling in love with Brennan showed Skye a world she'd been taught couldn't exist. Since then she's saved his life multiple times, and dealt a severe blow to the Society in the process, but all is not as it seems. Skye's nanites continue to adapt at an astonishing rate, making her quite possibly the most dangerous person on the planet, but fighting a guerrilla war against her former masters involves situations she's not prepared for, situations where she won't be able to save everyone, situations where she's no longer sure she's fighting on the right side. Desperate to end the fighting, Skye sets off on her most dangerous mission yet, and what she'll learn this time may very well destroy her.

Escaping the Society’s high-tech enclave the first time cost Skye both her mother and her innocence. Going back required the betrayal of Brennan and everything Skye loved. Now Skye is back on the outside. She’s on the run, isolated and hunted by new horrors that threaten the entire world. The fate of humanity hinges on Skye finding Brennan, but doing so while being chased by the entire might of the enclave’s military may prove too costly, even for Skye.