Lillian Kaufman hasn't heard from her twin sister since Eleanor left for a mysterious job at an Army base somewhere in Tennessee. Then she learns that Eleanor is missing. Lillian leaves New York to sneak into the mysterious town of Oak Ridge, only to learn that Eleanor has vanished without a trace-and she's not the only one. But how do you find someone in a town so dangerous it doesn't officially exist? Forced to pretend to be Eleanor, Lillian finds herself in the epicenter of the gravest scientific undertaking of all time, with no idea who she can trust. And the more she acts like Eleanor, the more she loses her grip on herself.