The Eiger Sanction
The Eiger Sanction is a 1972 thriller novel by Trevanian, the pen name of Rodney William Whitaker. The story is about a classical art professor and collector who doubles as a professional assassin, and who is coerced out of retirement to avenge the murder of an old friend. The novel was made into a film of the same name in 1975, directed by and starring Clint Eastwood. Whitaker wrote a sequel entitled "The Loo Sanction". Plot. Dr. Jonathan Hemlock is an art professor and mountaineer. He is also a collector of paintings, most of them obtained from  the black market. To finance his collection, Hemlock, who served in a Special Forces team of the Army Intelligence Branch and fought in the Korean War, works as a so-called "counter-assassin" for a secret US government agency, the CII. In order to acquire a Pissarro, Hemlock agrees to carry out a couple of "sanctions" (contract assassinations targeted specifically against killers of American agents). The first one is easily dealt with in Montreal. For the second, he will need to join a group of climbers who are about to attempt the north face of the Eiger, a particularly difficult  challenge. Hemlock goes back into training and eventually climbs the mountain with the team that he believes includes his would-be victim — whose identity he will have to deduce on the mountain itself. Poor climbing conditions disrupt the climb and lead Hemlock to the discovery that his target is someone other than he had expected.