A squadron of American warplanes, armed with gas developed by Corsican chemist Gannimer (dubbed "Napoleon Gas") flies to Leningrad. American workers inform soviet comrades about the impending catastrophe. But the air attack on the city has already begun, and the assault troops of the enemy capture one suburb of the city after the other. The Red Army is organizing the defense and reflects the attack of the enemy with gas-armed drones
Engineer Dukalsky arrives from Moscow on the instructions of an underground anti-Soviet center to the Baltic Shipyard in order to take possession of the blueprints of a powerful ship engine. The pest meets the author of the project - a young and incorruptible self-taught master Ivanov. After a series of unsuccessful attempts to buy out or steal the drawings from the author, Dukalsky decides to take Ivanov with him. Criminal Investigation Officers will attack the trail of criminals.
