Robert Ludlum's The Janson equation

the long version

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.