Illustrations -- Acknowledgments -- Introduction: The Secret History of the Civil War in the North -- 1: "Secret Secessionism in Our Midst"-The Failure of Civilian Investigations in the Old Northwest, 1861-62 -- 2: Investigating Desertion and Disloyalty- Henry B. Carrington and the Knights of the Golden Circle in Indiana, 1862-63 -- 3: "They Are Doing Us an Immense Amount of Good" -- 4: An Odious System of Espionage- The Intelligence Network Created by the Enrollment Act, 1863 -- 5: Watching "Mr. Jones"- Army Surveillance of Clement L. Vallandigham, the Ohio Gubernatorial Election of 1863, and Plots to Release Confederate POWs in the Fall of 1863 -- 6: "It Is Impossible to Doubt This"- Army Intelligence in the Northern Department in Early 1864 -- 7: "What I Say about Secret Dangers Is Well Considered and Based on Fact"- How Rosecrans's Detectives Infiltrated the Secret Organizations in Early 1864 -- 8: "When Government Determines to Act"- How Carrington's Detectives Infiltrated the Secret Organizations in 1864 -- 9: "I Feel Provoked beyond Measure at the Indifference of the President"- Convincing Lincoln of the Danger of Insurrection, Summer 1864 -- 10: A "Narrow Escape from a Civil War"- The Triumph of Military Intelligence in August 1864 -- 11: "I Make No Assertions without Proof"- Preserving the Northwest in the Fall of 1864 -- Postscript: The Evidence of Conspiracy -- Abbreviations -- Bibliography -- Index.