Ex-government agents appear to be Wal-Mart's investigators of choice. The retailer has emailed job listings to members of the Association for Intelligence Officers as well as posted ads on its site seeking to hire "global threat analysts" with backgrounds in intelligence. The job description for the analysts, who would have reported to a former Army intelligence officer, entailed collecting information from "professional contacts" to gauge threats from "suspect individuals and groups." In practice, their responsibilities would have extended to gathering information about Wal-Mart employees, suppliers, and customers; Wal-Mart monitors shoppers for suspicious or potentially criminal activity. A Wal-Mart spokesman said the company does not comment on security matters.

Roehm sued the retailer for breach of contract over her firing but dropped her case in November. She has denied all wrongdoing, including the affair.

Sam Morgan, Roehm's lawyer, declined to discuss the suit. But corporate espionage is becoming almost as sophisticated as government spying. Morgan said, "There is no right to privacy in the private-sector workplace."

Roehm and Womack were unwittingly drawn into a new world of intrigue in which rivalries between superpowers have been replaced by global competition among the titans of capitalism, where companies use the most advanced techniques available to scrutinize competitors and employees alike. From New York and London to Moscow and Beijing, today's corporations are venturing into a netherworld populated by former agents who have been schooled in the arts of detection and deception by the C.I.A., the F.B.I., Britain's secret services, and the former Soviet Union's K.G.B.  Instead of probing for state secrets or recruiting government ministers as double agents, these latter-day George Smileys are selling their old skills and contacts to multinationals, hedge funds, and oligarchs. They're digging up dirt on competitors, ferreting out internal corruption, and uncovering secrets buried in the pasts of job applicants, boardroom rivals, and investment targets.

The best estimate is that several hundred former intelligence agents now work in corporate espionage, including some who left the C.I.A. during the agency turmoil that followed 9/11. They quickly joined private-investigation firms whose U.S. corporate clients were planning to expand into Russia, China, and other countries with opaque business practices and few public records, and who needed the skinny on international partners or rivals.