At the start of the Last World War, on the Maginot Line, a troop of French soldiers awaited the German invasion.

A young aspirant (Lieutenant Grange / Humbert Balsan) was assigned, in October 1939, to command a stronghold located near a hamlet on the Belgian border, in the Ardennes forest. Reserved, friendly and conscientious, the young officer obeys orders from the hierarchical chain with a zeal devoid of the slightest conviction. The mission of this stronghold is to destroy enemy tanks and provide information on the enemy's movements. With the midshipman, three men - a corporal and two enlisted men - form the garrison of the fort. Daily life, military routine, relations with the villagers occupy the four soldiers, who vaguely feel the terrible threat of death weighing on them and try to keep a little more happiness. There will be the meeting of the officer and the pretty villager Mona (Aina Walle). There is also nature that we can finally contemplate at leisure, from autumn to spring. The wonderful spring of May 1940 sacked by German troops.