Post Watergate paranoia? Not the reason Three Days of the Condor ranks one of my favorites.
You have Robert Redford, Faye Dunaway, Cliff Robertson, Max Von Sydow, John Houseman, Tina Chen all weaving this tapestry of "playing" each other with mistrust and intrigue. The sex scene between Redford and Dunaway leads you in to next morning's coffee where Dunaway,(a stranger before then), answers Redford with something like "Have I ever denied you anything?" That is enough to send your mind reeling!! Robert Redford's character development is subtle and pure! Think I will watch it again tonight.