The long-awaited summer has arrived! The Obolensky family moved to the dacha and enjoys the fragrant air, fresh greenery, and the chirping of birds. Brothers Dimka and Alyoshka go fishing and pick mushrooms. But unexpectedly the peaceful course of life is disrupted by a theft at a local museum. Paintings by famous artists have been stolen. The brothers begin their own investigation and are already close to a solution when Alyoshka is captured by bandits! Will he be able to get out of a dangerous situation with honor, and will his brother be able to come to his aid? This is a task for the real children of Sherlock Holmes!