It is set in a crumbling, depressed post-war Vienna, divided up by the Allied occupying forces - a city Reed knew well from his wartime experiences. Beautifully shot by Robert Krasker in atmospheric black and white, the city almost seems to be a character in the story. The insistent, haunting zither music is by Anton Karas, whom Trevor Howard discovered playing outside a restaurant in Vienna.
The film is further distinguished by several performances, particularly that of Orson Welles, who only took the part of Harry Lime to help finance his Othello and later regretted asking for a salary rather than a share of the profits. Curiously, David O Selznick, the American co-producer (with Alexander Korda), had wanted Noel Coward for the part. If Coward had played it, we would never have had the most famous lines in the film, written by Welles himself: "In Italy for 30 years under the Borgias, they had warfare, terror, murder and bloodshed. But they produced Michelangelo, Leonardo da Vinci and the Renaissance. In Switzerland, they had brotherly love; they had 500 years of democracy and peace. And what did that produce? The cuckoo clock!"
Greene dreamt up the part of the wicked but charming Harry Lime - the old schoolfriend Holly Martins (Joseph Cotten) searches for - after finding an envelope on which he had written, some time before: "I had paid my last farewell to Harry a week ago, when his coffin was lowered into the frozen February ground, so it was with incredulity that I saw him pass by, without a sign of recognition, among the host of strangers in the Strand." It was, of course, first a novel and then a screenplay, but it was one of the few Greene adaptations that was more successful on the screen than on the page.
There are at least two extraordinary sequences - the first showdown between Lime and Martins on the slowly revolving ferris wheel of an almost deserted fairground, and the chase through the sewers of Vienna that ends with Lime's death. Hitchcock could not have accomplished these sequences better, and there is no doubt that Reed owed some debt to him.
Perhaps melodrama is never very far away, and the romance between Martins and Anna Schmidt (played by Alida Valli), once Lime's girl, could be seen as stretching the film a little too far in the direction of Casablanca. But we shouldn't forget the serious core of the film, which embodies in the figure of Harry Lime the corruption and exploitation of the post-war years in central Europe. Lime was, after all, a precursor of the contemporary drug dealer, a fact that makes the film oddly relevant today.