The story is about an American pulp fiction writer, Holly Martins (Joseph Cotten), who arrives in Vienna only to be confronted with the terrible truth that his one-time best schoolfriend Harry Lime (Orson Welles) has just been killed in a car accident, British police officer Major Calloway (Trevor Howard) adding that he was also one of the city's worst racketeers. Refusing to acknowledge Harry's involvement in criminal activities, he sets out to clear his friend's name. The story takes a new turn when Harry's porter tells him of a “third man” present at the time of his friend's death. Convinced that there is something wrong with his friend's accident he becomes determined to solve the mystery. The ensuing quest brings in Harry's dubious Viennese associates, the international police, all sorts of local types and Anna Schmidt, the truthful sweetheart of sinister Harry Lime – who eventually emerges from the darkness of a doorway as the the missing “third man”.