Leningrad, spring 1942. After the first winter of the blockade, the conductor of the large radio symphony orchestra receives an order from the government to perform Shostakovich's Symphony No. 7 in the besieged city. This seems impossible: only a few musicians remain from the orchestra. Some died of hunger, others went to the front, still others disappeared. But the concert must take place and resound throughout the world so that both friends and enemies can hear: "Leningrad is alive!" To help the conductor Karl Eliasberg, KGB agent Anatoly Seryogin was dispatched. But the fate of Lieutenant Seryogin, who had lost his entire family in an air raid, had already crossed paths with Eliasberg; it was Seryogin who had led the arrest of the conductor's wife. Despite their mutual distrust and hatred for each other, the conductor and the lieutenant had to accomplish the impossible: to find the missing performers in the besieged city and to perform the premiere of the Seventh Symphony in Leningrad.