Bolt — Dick Francis

In Kit Fielding's breakneck world of steeplechase racing, the ultimate catastrophe strikes: someone is shooting horses with a weapon fiendishly called a "humane killer." Kit must stop the murdering madness, and everyone in his upper-crust circle becomes a suspect--the princely rival who's trying to woo his woman, the personal enemy bent on ruining Kit's family, the black-market arms dealer whose plans could imperil the globe. Such dire situations call for drastic measures that a civilized man like Kit must steel himself to use....