Major Smith, a British intelligence officer, receives an assignment to transport to England a professor of the University of Bucharest, a geologist who has discovered a deposit of uranium ore in Romania. However, the professor suddenly disappears. To find him, the British devise a complex operation. In turn, German intelligence decides to use the results of the British. But there is a third interested party - Romanian patriots. They are relentlessly following the actions of the two intelligence agencies, trying to protect the professor and his discovery. With their help, the Romanian police commissioner manages to arrest the whole gang of spies.