The story takes place in the first days of the Great Patriotic War in the Northern Fleet. The young lieutenant Sboev is seconded aboard the old steamship Onega to accompany a cargo of weapons. In addition, the ship takes on board a group of prisoners who are being taken to the construction of a military airfield. While traveling to their destination, some of the prisoners plan to seize the ship and flee to Norway. A riot on the high seas is always scary. The hatred of prisoners and guards towards each other has been accumulating for decades. This hatred overwhelms people. A prisoner riot on a ship is doubly scary. Too much hatred in a limited space. But everything changes when a common enemy appears...