[2] The film is based on the true story of Albanian-born Elyesa Bazna, a spy with the code name of Cicero who worked for the Nazis in 1943–44 while he was employed as valet to the British ambassador to Turkey, Sir Hughe Montgomery Knatchbull-Hugessen.

In neutral Turkey in 1944, German ambassador Franz von Papen meets countess Anna Staviska, a Frenchwoman and the widow of a pro-German Polish count.

Ulysses Diello approaches the German embassy attaché Moyzisch, offering to provide von Papen with top-secret British documents for a price of £20,000.

Colonel von Richter is sent to Ankara to take command of the negotiations with Cicero, while the British send counterintelligence man Colin Travers to identify the spy.

Anna's newly found wealth and previous willingness to become a spy cause her to fall under suspicion by Travers, who also rigs the ambassador's safe with a burglar alarm.

Von Richter requests a document detailing an Allied operation called Overlord, the D-Day invasion plan, and Cicero demands £40,000 for it.

Diello escapes alone to Rio, where he enjoys a new life of prosperity and freedom until Brazilian authorities arrest him because all of his money is counterfeit, created during Operation Bernhard.

[6] In a contemporary review for The New York Times, critic Bosley Crowther wrote: "Those who may fear that the old days of silken spy films are as dead as the gone days of diamond tiaras and princely diplomacy can now settle back in the comfort and the tingling satisfaction to be had from Twentieth Century Fox 'Five Fingers' ... For here, in this literate entertainment Joseph L. Mankiewicz has made with a cast that might well have been recruited at an embassy function in pre-war Berlin, is as dandy an espionage thriller as ever went through the polished hands of a Grahame Greene or an Alfred Hitchcock—or for that matter, an E. P.