On July 6, 1975, a 3-year-old filly named Ruffian was loaded into the starting gate at Belmont Park for a televised match race against Kentucky Derby winner colt Foolish Pleasure. Since winning her first race a little more than a year earlier, the unbeaten, unflappable Ruffian had literally raced her way into the hearts of a nation. One of those hearts belonged to Newsday turf reporter William Nack. As a boy in Illinois, Nack had carried in his pocket a trading card of his hero, Swaps, the winner of the 1955 Kentucky Derby. As a young soldier in Vietnam, Nack tuned out the midnight bomb blasts by listening to racetrack broadcasts from Santa Anita. Now, fresh off the publication of his astonishing biography of Secretariat - described by Seabiscuit author Laura Hillenbrand as "the gold standard of horse books" - he found himself smitten once again. But tragedy struck that summer"s day at Belmont Park. After charging from the gate, Ruffian stumbled and shattered her right...