The author of the "magnificent...complex, vivid" (New York Journal of Books) Sin Eater returns with a rousing and propulsive novel based on the astonishing true story of the first female Pinkerton detective whose next assignment could end the Civil War. Kate Warne is many things: the country's first female detective, a Pinkerton agent, and a union spy. It's August 1861, and her latest assignment could finally end the bloody war and bring the fractured United States together again. All she has to do is win the trust of her captive: Confederate spy and socialite Rose Greenhow. But with Rose well aware of Kate's working-class background and belief in abolitionism, it seems an impossible task. Worst, Kate has secrets that make her vulnerable, such as her forbidden love affair with a colleague. With time running out, Kate faces not only the moral and political divides between herself and Rose but also the ones she made in her own heart and life. Can she make the difficult decision over which divides are worth crossing? Or will she fail the most important assignment of her career in this spellbinding and moving new novel from Megan Campisi?