As thoroughly examined as the Civil War and the assassination of Abraham Lincoln have been, virtually no attention has been paid to the life of the Union cavalryman who killed John Wilkes Booth, an odd character named Boston Corbett. Corbett became an instant celebrity whose peculiarities made him the object of fascination and derision. A hatter by trade, he was likely poisoned by the mercury then used in the manufacturing process. He was one of the first volunteers to join the US Army in the early days of the Civil War, a path that would land him first in the notorious Andersonville prison camp and eventually in the squadron that cornered Booth in a Virginia barn. The Madman and the Assassin is the first full-length biography of Boston Corbett, a man thrust into the spotlight during a national news event—an unwelcome transformation from anonymity to celebrity.