This movie was made and released about four years after its source novel of the same name by author Helen MacInnes was first published in 1963. This is the third of four screen adaptations of one of Macinnes' novels. The others are The Salzburg Connection (1972), Above Suspicion (1943) and Assignment in Brittany (1943).
Actor Robert Vaughn was cast in the lead role in this picture by MGM in order to capitalize on his popular Napoleon Solo spy TV character from The Man from U.N.C.L.E. (1964). This movie is Vaughn's only '60s spy film outside of playing Solo in the series and other associated projects. Since the title of every episode ended with the word 'affair', this film could easily be mistaken for being an U.N.C.L.E. adventure, or for being one of the many theatrical version which were edited together from several episodes, however, none of the U.N.C.L.E. 'movies' used the word 'Affair' in it's title, only the episodes.
The two movies that Italian actress Luciana Paluzzi starred in straight after the James Bond film Thunderball (1965) were also both spy films, this picture and The One Eyed Soldiers (1967).
First theatrical feature film directed by Jerry Thorpe. Thorpe mostly worked in television except for this film and Day of the Evil Gun (1968) made and released a year later.
Movie writer/producer E. Jack Neuman has an uncredited role as the suicidal American diplomat at the beginning of the film.