THE THIRD MAN had a lot of heavyweights involved in it’s production. Produced by Alexander Korda, David O. Selznick, and an uncredited Carol Reed, the script was written by Graham 
The cast had Joseph Cotten as Holly Martins, an out of work pulp western writer who comes to post-war Vienna at the invitation of his childhood friend Harry Lime(Orson Welles) for a job writing for his medical charity. Trevor Howard is a policeman, Major Calloway, and Alida Valli is Anna Schmidt, the lover of Lime. A very young Bernard Lee(M in eleven Bond films) is police Sgt. Paine.
Post-war Vienna is divided into four sectors ruled by the four Allies: The United States, Great Britain, France, and Russia. Each is tightly controlled. No walls are up like in Berlin, but access is hard.

Everyone seems to want him out of the country as soon as possible until he meets a gentleman from a group starved for culture in this former German controlled city. though he’s never heard of him, Paine reveals he’s a writer from the States(Paine loves his westerns). They agree to put him up so that he can do a talk and answer questions.
It’s the excuse Holly needs. Something doesn’t smell right. Calloway had intimated that Harry Lime was a racketeer, which Holly didn’t buy though he hadn’t seen Harry since 1939.
Who was this third man?

Holly keeps investigating and when he goes to speak to the porter again finds him murdered. The neighbors think he did it and the police have to hustle him off. He’s convinced to leave finally. He wants to help Anna Schmidt though, who he’s sort of fallen for when he’s visited her a few times. She’s in trouble for a forged passport that Harry gave her and is to be deported to the Russian sector.
Then Holly discovers who that third man is and everything is turned upside down. The explosive climax in the sewers of Vienna and the completely unexpected ending made for a fine 
Filimg was done in Vienna and that old world look gave it a better feel than sound stages in Hollywood.
A bit on Graham Greene. He wrote the novella to get a feel for Vienna. It was never intended then to be put out for public consumption. The narrator in the novella was Major Calloway. The emphasis was different and the ending was more what I thought the film might be. Boy was I fooled.
And finally the music score. Carol Reed didn’t want heavily orchestrated pieces and happened to be in a small club one night when he heard Anton Karas playing his zither. It sounded right and he got the job.
As always. check out Todd Mason for other movies and related stuff.