A Red Army officer Polevoy possesses a navy dirk with a secret message encrypted in its handle. The second part of a message belongs to a White army officer Nikitskiy. It's up to three young friends of Polevoy to uncover the mystery.

Three friends in a summer camp are looking for a treasure hidden in a old mansion.

This is a last of 3 movies about 3 friends (the other two are "Kortik" and "Bronzovaya Ptitsa"). The gang has grown up and in this movie they discover and help to stop criminal activity on the factory and in their neighborhood.