The Kremlin Letter (1969) DVD

In this star-studded, black-hearted spy thriller directed and co-written by the legendary John Huston (The Maltese Falcon, The African Queen), a potentially catastrophic diplomatic letter from the CIA must be recovered at all costs. Drafted in is Rone (Patrick O'Neal), a young agent with a photographic memory, to make his way through a treacherous maze of shadowy cities and shady characters.
Based on the acclaimed novel by Noel Behn, drawn from his work within the U. S. Army Counterintelligence Corps, The Kremlin Letter is a brutal, level-headed examination of espionage, leaving behind any trace of gadgetry or glamour.