Robert Ludlum's (TM) The Janson Equation (Janson series)

To prevent a war in Asia--one that could quickly spread to the rest of the world--Paul Janson and Jessica Kincaid must learn the truth behind a young woman's murder...
Prominent U.S. Senator James Wyckoff hires former government agents-turned-private security consultants Janson and Kincaid to locate his teenage son Gregory. Gregory's girlfriend Lynell has been found strangled in a Seoul hotel, and Gregory has fled the city to avoid being arrested for the crime. But Senator Wyckoff insists that his son is innocent, suggesting that Lynell, who was a translator, may have been murdered because of something she overheard at a recent international conference. And when Janson and Kincaid realize they're being hunted by an assassin, they suspect that this crime--and the cover-up--were orchestrated by a shadowy unit of the U.S. State Department as part of a larger plot to provoke violence between North and South Korea.