The sport of kings and Seabiscuits rides on the back of its pawns. With intertwined portraits of three Louisiana jockeys—a young up-and-comer, a broken down former great, and a retired jockey who has become a jockey’s agent—the movie reveals the harsh, bulimic secrets of the men in silks. That horse racing is dangerous is no great surprise, but the insidious reasons why are in turns fascinating and repelling.  RR