Detective novelist Charles Latimer becomes fascinated with the dead villain Dimitrios and on a whim begins to investigate Dimitrios's life. His quest leads him to one of Dimitrios's former partners in the drug business, Mr. Peters, whom Dimitrios double-crossed and sent to jail. Mr. Peters reveals that Dimitrios is actually alive and convinces Latimer to help him blackmail the villain. The dangerous and witty Dimitrios, though, tracks his blackmailers down, and Latimer is lucky to escape the gun battle that kills both Peters and Dimitrios.

While mystery writer Charles Latimer is traveling in Turkey, he learns, by chance, about a criminal named Dimitrios who has turned up dead in the Bosphorus River. Latimer goes to the morgue and sees Dimitrios's body. He is curious about the criminal and decides to investigate Dimitrios's past to see what he can learn about the man. Latimer tracks Dimitrios from his first known crime, murder and robbery in Smyrna during the Turkish holocaust against the Armenians, to his immigration to Greece as a refugee, to Sofia, where he was involved in an assassination attempt.

In Sofia, Latimer discovers a man named Mr. Peters searching his room. Peters questions Latimer about his interest in Dimitrios and seems very interested when he learns that Latimer saw Dimitrios's body in the morgue in Istanbul. Peters offers Latimer a chance to make a lot of money, but he does not elaborate. He directs Latimer to an ex-spy to learn about Dimitrios's espionage activities, as an act of good faith, and asks Latimer to contact him in Paris.

After finding out about Dimitrios's involvement in the theft of plans to a minefield, during which he double-crossed the man who hired him, Latimer contacts Mr. Peters in Paris. Dimitrios was head of a drug-smuggling ring in Paris, and Mr. Peters was one of the management. Dimitrios turned his cohorts over to the police and fled when he became addicted to heroin and needed a cure. Peters tells Latimer that Dimitrios is alive. The dead man was also involved in the drug ring and tried to blackmail Dimitrios. Dimitrios killed the blackmailer and faked his own death.

Peters convinces Latimer to help him blackmail Dimitrios, although Latimer refuses to take any of the earnings. They successfully get 500,000 francs from Dimitrios, and Peters believes there is no way Dimitrios can track them down. Peters and Latimer are about to celebrate their victory over champagne before Latimer returns to England, when Dimitrios appears with a gun. He shoots Peters, but Latimer gets Dimitrios's gun away. Latimer gives Peters the gun and goes for the police, though Dimitrios warns him Peters will shoot him. Latimer barely gets out the door before he hears shots. Running back in, he finds both Latimer and Dimitrios dead. Latimer removes all traces of himself and leaves the bodies with the blackmail money. He heads back to his normal life.