One mislaid credit card bill or a single dangling e-mail message on the home computer would have ended everything: the marriage, the big-time career, the reputation for decency he had built over a lifetime. So for more than 10 years, he ruthlessly kept his two identities apart: one lived in a Westchester hamlet and worked in a New York office, and the other operated mainly in clubs, airport bars and brothels. One warmly greeted clients and waved to neighbors, sometimes only hours after the other had stumbled back from a "work" meeting with prostitutes or cocaine dealers. In the end,...