Judah Benjamin, the rebellion's Mephistopheles, Attorney General, Secretary of War and State and spymaster of the C.S.A., created a Mona Lisa in the black art of espionage. Lincoln's reluctant general, George McClellan, A.P. Hill, one of Lee's favorite generals and Nelly Marcy McClellan, George's wife and Hill's clandestine lover were transformed from a love triangle into a spy network. Hill and Nelly softened George for Benjamin's pitch that hooked...