Our contemporary, a naval officer, finds himself in the consciousness of the commander of the monitor "Udarny", a ship of the Danube flotilla, in 1940, just before the start of the Great Patriotic War. And now he is Ivan Prokhorov, senior lieutenant. Knowledge, and most importantly, understanding of the reasons for the initial failures in the war force him to introduce new methods of combating enemy aircraft. Unable to reveal the origin of information and knowledge, Prokhorov has to take risks... For him, equipment and technology, and against - geniuses from intelligence and war.