A British spy infiltrates the Gestapo hierarchy.

In 1939 Berlin, as Europe teeters on the brink of war, German supply officer Alex Schottland wins the respect of Adolf Hitler for his acumen in dealing with supply issues. At a party to celebrate his promotion to general, Schottland encounters Lili Geyr, an Italian singer popular with the German troops, whom he has met several times before. When Lili accuses Schottland of continually avoiding her, he excuses himself from the party and visits Cornaz, the owner of a clock shop. There, Schottland, a British spy who has posed as a German officer for the past twenty-four years in order to relay topsecret information to the British, complains to Cornaz, his contact, that he longs to discard the masquerade that makes him feel like a "clock without a face." Cornaz commiserates with Schottland, but insists that he return to the party and continue his charade. In the ensuing years, German troops sweep across the European continent. One day, Schottland comes to the shop to tell Cornaz that the Germans have decided to postpone their invasion of England and attack Russia, a decision that delights Cornaz who believes that German aggression will bind Russia to the West. Schottland has recently been appointed deputy chief of supply, and when he suggests using his new position to sabotage German military supplies, Cornaz reminds him that his mission is to obtain information, not sabotage military installations. Capt. Reinisch, Schottland's envious and suspicious aide, has discovered that Schottland has changed his name from Scotland and is of British paternity. When he reports this information to his superiors, however, they scoff that they are aware of Schottland's dual nationality and point out that Schottland has been a German officer too long to be considered a spy. Schottland's information has allowed the Allies to steadily destroy German supply depots, causing the Germans to wonder from whom they obtained their intelligence. To deflect suspicion from himself, Schottland suggests that "defeatists" among the German staff have been leaking information to the enemy. One day, Cornaz furtively approaches Schottland to warn him that their courier has been arrested. Cornaz, thinking that he may be next, tells Schottland that if something happens, he will find his new contact by answering a newspaper ad for an antique watch known as the "Nuremberg egg." The contact will identify himself by offering to sell the time piece for ninety marks. Soon after, Cornaz is arrested and Schottland, a frequent customer at the watchmaker's shop, is summoned to headquarters for questioning. There Schottland is forced impassively to watch as zealous Gestapo Leader Mueller tortures Cornaz to death. Because Cornaz had top secret information in his possession, Mueller arrests Schottland for treason, but he is soon exonerated and released by Gen. Kaltenbrunner. While studying the personal ads one day, Schottland sees two ads for the Nuremberg egg. When the first seller fails to name the correct price, Schottland proceeds to the second address and is stunned when Lili answers the door. Reinisch, who is in love with Lili, is visiting, and consequently, Schottland leaves after ascertaining that Lili is his new contact. After Reinisch has gone, Schottland returns and tells Lili that he is attracted to her. Insisting that their relationship must remain impersonal, Lili suggests that they pretend to be lovers as a cover for their frequent meetings. Lili decides to relay Schottland's latest message in a song she is to perform on a radio broadcast. When Lili is unexpectedly replaced by another singer, Schottland, concerned, rushes to her apartment. Once assured that Lili is safe, Schottland, who has been ordered to the front, decides to transmit the message when he reaches the battle line. At the front, as Schottland begins to broadcast his information, a German corporal approaches him. Schottland shoots the corporal and the rest of his patrol when they come to investigate. The corporal survives, however, and before lapsing into a coma, tells his superiors about the German general with the transmitter. Upon returning to Berlin, Schottland informs Lili that he has failed and, now unable to transmit important information, has decided to resort to sabotage. Over the next few months, Schottland cunningly tricks Hitler into making strategic military blunders. After the Germans lose the Battle of the Bulge, Schottland conceives of using Lili's popularity with the troops as an excuse for her traveling to the Western front. From there, she will be able to sneak across the border and deliver the information to the Allies. Upon reaching the front, Schottland gives Lili a map laying out her escape route and promises to take her to his favorite English country inn once the war ends. That night, as Lili makes her way through the woods, she is stopped by Reinisch, who confiscates the map, then shoots her. Meanwhile, in Berlin, the corporal has regained consciousness and is being questioned by Mueller. Determined to prove that Schottland is a spy, Mueller shows the corporal his photograph, but when the soldier states he is only able to identify the man's voice, Mueller decides to arrest Schottland as soon as he returns to Berlin. Unaware of Lili's fate, Schottland goes to his Berlin apartment, accompanied by Reinisch. There Reinisch throws down the map, pulls out his gun and declares that he intends to kill the treasonous Schottland. Realizing that Reinisch killed Lili, Schottland attacks him, and as they wrestle for the gun, the weapon discharges, killing Reinisch. Schottland then goes to see Hitler, and after naming Mueller as one of the "defeatist" generals who oppose the Führer, leaves for the front. Mueller, who has been informed of Reinisch's death, sends a motorcycle brigade after Schottland. Upon seeing the brigade trailing them in the distance, Schottland orders his driver to turn the car around while he continues on foot. Running into the woods, Schottland is soon captured by Allied soldiers. Once Germany has been defeated, Schottland, now wearing the uniform of the British army, visits the inn where he was to meet Lili.