Trevanian

Jonathan Hemlock lives in a renovated Gothic church on Long Island. He is an art professor, a mountain climber, and a mercenary, performing assassinations (i.e., sanctions) for money to augment his black-market art collection. Now Hemlock is being tricked into a hazardous assignment that involves an attempt to scale one of the most treacherous mountain peaks in the Swiss Alps, the Eiger.
In a breathtakingly suspenseful story that is part thriller...

In a prequel to Trevanian's "Shibumi," amid the chaos of the Korean War, the CIA offers Nicholai Hel his freedom only if he kills the Soviet Union's Commissioner to China in Beijing, a mission that draws on all his strengths.