A deformed thumb, a neck scar from a stage accident, and a broken left leg, the result of a dramatic leap. These were the telltale markings that for decades identified a sideshow attraction as the supposed body of John Wilkes Booth. They persuaded onlookers that Lincoln's assassin was not killed in 1865 but survived the assault on Garrett's barn to live on as a fugitive for thirty years afterwards. As Wyatt Evans shows, some popular stories, no matter how weird and improbable, simply refuse to die.

Evans recounts how a mummified corpse came to embody the romantic image of the assassin and...