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 American agent. 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.