Anti-Soviet propaganda film about the activities of the Soviet Secret Police (GPU) in Western Europe in 1939/40: the violin virtuoso Olga Feodorowa (Feodorova) works undercover for the GPU. She recognizes the leader of the GPU Europe Section, Nikolai Bokscha, as the man responsible for the death of her family amidst the chaos of the Russian revolution. She denounces Bokscha, who works as a double agent for the French at the GPU Headquarters in Moscow, upon which she is accused of disloyalty. As the GPU do not want to release her from service, she takes her own life.