Abraham Lincoln was watching a play at Ford's Theatre when a gunman crept up from behind and fired at the president's head. As Lincoln crumpled with a terrible wound, the shooter leapt from the balcony and fled before a shocked audience. He was John Wilkes Booth, a well-known stage actor, and he imagined himself a hero avenging the South's defeat in the Civil War. Soldiers searched for Booth as Lincoln suffered long hours before dying. There would...