The Germans are advancing on Tallinn, and will soon push through the city's defenses. At the same time, they trap the Baltic Fleet with new depth mines. The Germans' goal is to inflict maximum damage during the evacuation of the Baltic. Kuznetsov has to discover the new German depth bombs and find out on which fairway they are located.

The Germans managed to completely encircle Sevastopol from the land, the situation in the city is difficult. Not enough manpower and ammunition. Urgently need countermeasures. Stavka proposes to land a naval landing in the Kerch Peninsula. This will force the enemy to pull back some of its forces from Sevastopol, and the city will allow to accumulate forces and prepare for defense. However, the operation raises serious doubts in Kuznetsov's mind, and may prove to be a failure.

The "Road of Life", which brings supplies to besieged Leningrad, is under threat. The Germans have high-speed torpedo boats of a previously unknown modification, they sink barges with bread. Kuznetsov is assigned to discover the base of the boats and take measures. But first he has to endure a confrontation with Deputy Commissar of Defense Mekhlis.

River transports on the Volga are attacked by new magnetic-acoustic mines. The defense of Stalingrad is threatened. To help our engineers deal with the new enemy mines, Kuznetsov and Beria combine their intelligence. They have the difficult task of transferring a Soviet spy from Germany - engineer Zinaida Stern, who will be engaged in the development of new anti-mine minesweepers.

The Red Army has seized the initiative and is successfully beating the enemy. But the situation in the Baltic remains difficult. The fleet is blocked in Kronstadt and has no way out to the operational space. The Germans tightly mined the exit from the bay. The enemy has technical superiority, while many Soviet specialists are imprisoned. Kuznetsov reports to Stalin on the need to create a naval center in Kronstadt on the example of Tupolev Design Bureau - the so-called "sharashka". But Kuznetsov's idea is resented by Beria.

Nikolai Gerasimovich Kuznetsov - the youngest in the history of our country People's Commissar, who headed the Soviet Navy shortly before the Great Patriotic War. The young Commissar will have to confront an experienced and cunning opponent - Commander-in-Chief of the German Navy Erich Reder. The difficult situation at the front will require Kuznetsov to immediately make risky and even daring decisions, on which will depend the fate of many battles.