Carol Reed's The Third Man.
"The most famous collaboration of the director Carol Reed and the screenwriter Graham Greene has the structure of a good suspense thriller and an atmosphere of baroque, macabre decadence. The simple American, Joseph Cotten, arrives in postwar Vienna to meet an old friend, only to be told that the friend has been killed in an accident. In trying to discover the facts, Cotten learns so much about his friend that when he finally finds him alive, he wants him dead. Orson Welles' portrait of the friend, Harry Lime, is a study of corruption--evil, witty, unreachable. It's balanced against Trevor Howard's quietly elegant underplaying of the Army officer who teaches the simple American some of the uglier facts of life. There is an ambiguity about our relation to the Cotten character: he is alone against the forces of the city and, in a final devastating stroke, he is even robbed of the illusion that the girl (Alida Valli) is interested in him, yet his illusions are so commonplace that his disillusion does not strike us deeply. Greene has made him a shallow, ineffectual, well-meaning American. Robert Krasker's cinematography won the Academy Award. The zither music is by Anton Karas." — Pauline Kael