A group of 6th grade school children master their everyday lives. Van'ka has inventive talent, but he can't cope in class. His loyal friend Aleša tries to protect him. The curious and ambitious Katja thinks Van'ka is lazy, but she also has some problems at school due to her great commitment to the pioneer group, of which all three of them are members. Will Van’ka and Katja successfully complete the school year or have to repeat the 6th grade?

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.

1941 year. The flagship of the head detachment of the Black Sea Fleet gives an order to one of the submarines to remove the crew from the damaged torpedo boat. An enemy cruiser discovers a Soviet submarine and bombards it with bombs. Submarine forced to lie down. But the task will be completed - and the enemy will take flight.