On June 21, 1941, a few hours before the war, a graduate of the border school, Lieutenant Kolya Pluzhnikov, a former Moscow schoolboy, finds himself in the border Brest and in one of the restaurants he meets the cook of the commander's canteen. Kolya and his night companion Mirra slowly return to the unit along the streets of Brest.
And in the morning, Lieutenant Nikolai Pluzhnikov takes command of the garrison and takes the first battle with the Nazis. When he finds himself face to face with the enemy, Mirra will become his guide and assistant, knowing perfectly well the exits to the fortress.