This film remains one of my all-time favorites, and every once in a while I have to track down a viewing and see it again. It brings back its era with great immediacy for me --- WWII was thirty years in the past, the Cold War was on. The war in Vietnam was over, but way too late. The complicated plot plays out as an extension of a haunting backstory. The women are charismatically desirable. The bad guy is despicable.
Keeping up with the plot and figuring out characters' motivations is an enjoyable challenge, and becomes itself "the game" for the viewer. Set in Switzerland around Bern, it's a great city to visit in those days.
Check out the credits: Screenplay by Durrenmatt; Directed by Maximilian Schell. The cast includes Robert Shaw, John Voight, Donald Sutherland and Jacqueline Bissett.