The means used by foreign spy services to obtain the trade secret of a French invention.

One morning in August 1944, the inhabitants of a French village are celebrating their premature liberation. The festivities are interrupted by the arrival of an exhausted, leaderless German detachment. A few kilometers away, the inhabitants of the village of Muzière negotiate with the Germans and agree to a truce. But the arrival of a Wehrmacht captain, anxious to regain control of the men, puts an end to this fragile peace process. The captain suggested meeting the Americans and surrendering to regular troops rather than civilians. The inhabitants of Muzière, believing the truce to be broken, fire on the Germans and, on this misunderstanding, the guns start talking again.

Pascal and Martine are married, have children, but are getting bored with each other. Pascal is tempted by a beautiful salesgirl with whom he finally has a date. But the bombshell promised more than she actually delivers. On the other hand, he is attracted to his precocious niece Sophie. But he only becomes her confidant, living vicariously her first sentimental experiences with boys of her age. On her part, Martine winds up responding to the advances of her office manager who has been trying to pick her up for months. She follows him to his apartment but the alleged Don Juan is nothing but a boor who prefers to watch a soccer match rather than to make love to her. In frustration, she leaves him sprawled before his set while she returns to Pascal. They realize their extramarital experiences have reinforced their couple and can now live happily ever after.