1942, Polar region. The Germans are preparing to capture Murmansk. The submarine Sch-721 is considered lucky, and its captain Aleksei Strogov has the ability to extricate himself from the most difficult situations. He also develops tactics for a periscope-free torpedo attack, despite the skepticism of colleagues and management. And now, when the Happy "Pike" had to take on board the crew of another Soviet submarine, and she was on the seabed with almost no oxygen, Aleksei manages to save people and perform the operation, paying for it with his life...