In this book, Louisa Holmes, a lovely young woman living in Washington, D. C., is lured into the shady world of espionage by Dr. Gleason, a member of the infamous network of physician-spies. Innocently, she accepts a mission: to obtain information from a handsome Confederate officer, Major Robert Petrie. Louisa is smuggled into the Confederates' capital city, and while General George B. McClellan and the Army of the Potomac struggle towards Richmond, she falls under the suspicious eyes of Confederates Dr. Hugh Ryle and his strange sister, Charleen. At story's end, Louisa struggles to escape the same fate as that of Union spymaster, Timothy Webster: imprisonment in Castle Thunder and death on the gallows.