Holly Martins, an American author of western fiction, arrives in post–Second World War Vienna (which has been divided among the Allies: the Americans, British, French, and Soviets) seeking his childhood friend, Harry Lime, who has offered him a job. Martins is told that Lime was killed by a car while crossing the street. At Lime's funeral, Martins meets two British Royal Military Police: Sergeant Paine, a fan of Martins's books, and his superior, Major Calloway. Afterwards, Martins is asked by Mr. Crabbin to give a lecture to a book club a few days later. He then meets a friend of Lime's, "Baron" Kurtz, who tells Martins that he and another friend, a Romanian called Popescu, carried Lime to the side of the street after the accident. Before he died, Lime asked them to take care of Martins and Lime's girlfriend, actress Anna Schmidt.

Martins goes to the theatre to meet Anna, quickly becoming suspicious that Lime's death was not an accident. Anna's secondhand account of the fatal accident that Lime's doctor just happened to be passing by and that he was run over by his own driver just seemed too hard for Martins to believe; even Anna thinks Lime's death may not have been an accident. The porter at Lime's apartment building says that Lime was killed immediately and that three men carried the body, not two. Martins and Anna discover that the police are searching her flat. They discover a forged passport, confiscate it and detain her. The next evening Martins visits Lime's "medical adviser" Dr. Winkel, who says that he arrived at the accident after Lime was dead and claims only two men were there.

The porter offers to give Martins more information, but someone kills him before Martins can talk to him. When Martins arrives with Anna, the crowd believes that he was involved and they become hostile, but they manage to escape the angry crowd. Martins returns to the hotel and a cab immediately takes him to the book club, where he makes a very poor speech. When Popescu enters, he asks about Martins's next book. Martins says that it will be called The Third Man, "a murder story" inspired by facts. Popescu tells Martins that he should stick to fiction. Martins then notices two thugs advancing towards him, so he flees on foot through the ruins of the bombed out city and manages to escape.

Calloway again advises Martins to leave Vienna, but Martins refuses and demands that Lime's death be investigated. Calloway reveals that Lime's racket was stealing penicillin from military hospitals, diluting it, then selling it on the black market, injuring or killing many. Martins, once convinced, agrees to leave.

Martins visits Anna that evening, learning that she has also been told through Calloway about Lime's crimes. Leaving her apartment, Martins notices someone hiding and watching from a darkened doorway. A shaft of light reveals the person to be Lime. Ignoring Martins's calls, Lime flees and vanishes. Martins summons Calloway, who deduces that Lime has escaped through the sewers. The British police exhume Lime's coffin and discover that the body is that of the orderly who stole the penicillin for Lime. Anna is about to be ordered to the Soviet sector and is questioned once again by Calloway.

The next day, Martins meets Lime and they ride Vienna's Ferris wheel, the Wiener Riesenrad. Lime obliquely threatens Martins, reveals the full extent of his ruthlessness and then reiterates his job offer before leaving quickly. Calloway then asks Martins to help capture Lime. Martins agrees to help only on one condition, demanding in exchange Anna's safe conduct out of Vienna. Martins and Anna meet. She learns of the plan, but wants no part of it. Exasperated, Martins decides to leave, but on the way to the airport, Calloway stops at a hospital to show Martins a number of children crippled or dying of meningitis, who were treated with Lime's diluted penicillin.

Lime arrives at a small cafe to rendezvous with Martins, where Anna warns Lime that the police are closing in. He tries once again to escape using the sewer tunnels, but the police are there in force. Lime shoots and kills Paine, but Calloway shoots and wounds Lime. Badly injured, Lime drags himself up a ladder to a street grating, but he cannot lift it. Martins then kills Lime using Paine's revolver. Later, Martins attends Lime's second funeral. At the risk of missing his flight out of Vienna, he waits on the street to speak with Anna, but she ignores and walks right past him.
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== osoby ==			== profese ==
	Alexander Korda		Producent

cena	festival	ročník	osoba	nominace/cena
Nejlepší britský film	BAFTA	3 (1949)	Alexander Korda	cena
Nejlepší film z libovolného zdroje	BAFTA	3 (1949)	Alexander Korda	nominace