Second half of September 1939. Lt. Brejer, along with a detachment of his sappers, receives orders to blow up the bridge. The promised explosives do not arrive. So Brejer gets the order to withdraw and reunite with the rest of the division. Along the way, suffering hunger and discomfort along with his soldiers, he joins various divisions, collects survivors and fights. From a German prisoner of war, he finally learns that the Soviets have entered Poland. Finally, he and his men manage to reach his home unit, but that unit has just surrendered to the Germans.