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.