The story is about a brave boy who never takes off his hat.

The Soviet steamer Bogatyr delivers construction materials and rafts with timber to the earthquake-stricken city of Marto. However, foreign intelligence is preparing a sabotage operation on the Bogatyr...

A Soviet trading ship sank into the Italian port. Sailor Roman went ashore. In one of the squares he heard singing. It was sung by Francesca. The sailor was delighted with her voice and beauty. They wandered for a long time that day on ancient streets and squares. And the next morning the war began. The Soviet ship had to urgently return to their homeland. It was difficult to part in love, but they believe that they will definitely meet.

In one of the southern ports, state security authorities detained a spy with a plan for the object of sabotage — a floating dock, prepared for towing to a remote port. Major Lyudov, according to a number of signs, realizes that a whole group of enemies is operating in the city. With the help of Rakitina, the librarian of the floating dock, Lyudov and his assistant state security lieutenant Savelyev, they manage to unravel the tangle of espionage ties and prevent the crime.

A black child rescued from by Russian sailors, whom they name Maksimka, having overcome his fear of white people, turns out to be an unusually smart and kind little boy. The rude drunken sailor Ivan Luchkin was especially attached to the boy. Once it was Maksimka who managed to save Luchkin from foreign recruiters of labor. For resourcefulness and courage, the young hero is enlisted in the team of the corvette and becomes the cabin boy of the Russian fleet.