Film is set in 60s Leingrad, Russia. The main character Boris Lebedev (Demyanenko) is a young talented biomedical scientist. He is in love with the German student Sonya. This is used by the foreign intelligence agents to trap Boris Lebedev, and to blackmail him into cooperation with the foreign spy. But Boris Lebedev is not an easy victim. He is using his analytical mind to outsmart the enemy, and he wins.