In George Appo's world, child pickpockets swarmed the crowded streets, addicts drifted in furtive opium dens, and expert swindlers worked the lucrative green-goods game. On a good night Appo made as much as a skilled laborer made in a year. Bad nights left him with more than a dozen scars and over a decade in prisons from the Tombs and Sing Sing to the Matteawan State Hospital for the Criminally Insane, where he reunited with another inmate, his father...