“The mood of wry disillusion that seeps through the screen adaptation of Graham Greene’s novel ‘The Quiet American’ is sounded in the movie’s opening moments by the voice of Michael Caine musing dreamily on the mystique of Saigon in the early 1950’s. It is a place, declares his character, Thomas Fowler, where colors and tastes seem sharper than they do elsewhere and where even the rain has a special intensity. People who go to Saigon in search of something, he suggests in a silky murmur, are likely to find it. That something has everything to do with faraway places and a mirage of sex and adventure in an exotic clime. Fowler is a wistfully cynical British journalist who has fled an arid marriage in England to live in Southeast Asia, where he is reporting on the Vietnamese fight for independence from French colonial rule. His attitude toward the political turmoil…