Susy Tucker marks the time her autistic son, Zach, began hugging her again — after a lapse of four years — by the arrival of Clyde, a chocolate Labrador trained behind bars by a convicted killer. Within three weeks of Clyde’s arrival at the Tuckers’ home in Colorado Springs, Zach went from petting his dog to wrapping his arms around his mother. It was a stunning moment, one of many to follow. The boy who once grimaced and whined at any skin-to-skin contact had learned the warmth of touching from a dog. Zach and Clyde’s story is one of redemption — of how a rescue dog, a prisoner and a boy learned empathy and understanding from one another. Zach’s parents had run out of ideas and were skeptical when they stepped into the visiting room at the high-security Sterling pr...