A story about fantastic adventures of a fifth-grader Zhenya Ushakov on the island of Dvid.

June 21, 1941. Young lieutenant Kolya Pluzhnikov, having received an appointment to a permanent place of service, arrives in Brest. The crowded waiting rooms of the station and the crowd of people weighed down with luggage do not alarm the young man, filled with joyful hopes. Kolya hurries to the location of his unit - the Brest Fortress... The soldier does not have time to enlist in the personnel of the military, and at four in the morning artillery explosions are heard - the war has begun. He was not enlisted in the ranks of the military personnel of the Brest Fortress, but still took part in the first battle in his life, which lasted ten months.