The Eiger Sanction (1975)

Synopsis
Clint Eastwood both directed and starred in this thriller based on a novel by Trevanian. Dr. Jonathan Hemlock (Eastwood) is a professor of art history who formerly had a deadly secret life; he was a hired assassin working with an international intelligence organization. Normally content to collect and study art, Hemlock is forced by blackmail to perform one last hit, or, as the organization euphemistically calls it, a "sanction." The victim will be one of three men attempting a dangerous ascent of the Eiger, a beautiful but punishing mountain range in Swiss Alps. While Hemlock is an experienced mountaineer and willing to make the climb, he's troubled to discover that he does not know which of the other three men scaling the Eiger is his true target. The supporting cast includes George Kennedy and Jack Cassidy; the latter earned enthusiastic reviews for his over-the-top performance as a flamboyantly gay secret agent. ~ Mark Deming, All Movie Guide