About the lives of the crew members of the submarine "Varshavyanka". The crew members of B‑556 serve with dignity. The closed world of the submarine imposes its own conditions: there is no distinction between day and night here; you need to be on guard both day and night. But the sea prepares many unforeseen circumstances for the heroes. They will have to participate in rescuing a Russian tanker, help drowning fishermen, and assist oceanologists. Before that, the submariners will take on board the mysterious female pilot Galina, who was involved in a plane crash and ended up on the open sea. Her appearance on the submarine will stir up trouble in the hearts of some of the characters, and events will begin to unfold in an unexpected way.