During World War II, two French civilians and a downed British Bomber Crew set out from Paris to cross the demarcation line between Nazi-occupied Northern France and the South. From there they will be able to escape to England. First, they must avoid German troops – and the consequences of their own blunders.

Two young men, one shy and one self-confident, spend a fast-paced night in Paris trying to pick up chicks. They confront every possible difficulty

It is based on upon the memoir Mémoires d'un agent secret de la France libre et La Ligne de démarcation by Gilbert Renault under his pseudonym Colonel Rémy. A small village in the Jura is split by the river Loue which creates the line of demarcation between Nazi occupied France and freedom. A French officer, Pierre, is released by the Nazi soldiers to find his chateau converted into a German command centre. Whilst he is obliged to co-operate with the enemy, his wife Mary supports the resistance movement and is willing to risk her life for it. The Nazis step up their activity against the resistance, insisting that any who attempt to cross the line of demarcation will be shot. When his wife is arrested, Pierre decides to switch his allegiance.

The SS puts a slutty nightclub singer in charge of a train car full of prostitutes whose "services" are reserved solely for Adolf Hitler.

The exploits of Chief Police Inspector Chabrier, first before the invasion of France in May 1940 as he fights against spies preparing the coming the Germans, particularly Emmy de Welder, the alleged manager of the Rouen hospital. Later, Chabrier and his men go underground and resist the occupiers whatever the price to pay. When the Liberation comes Chabrier resumes his activities at the French National Police.

June 1944, a French town towards the end of the occupation. Following several attacks perpetrated by the resistance, the inhabitants who listen to English radio are rounded up by the Germans in a prison and considered as hostages. In one of the cells are found men from all walks of life: an aristocrat, the Viscount of Saint-Leu, Doctor Noblet, a resistance fighter, Béquille the wanderer with a wooden leg, and a strange character nicknamed "Black Market". The latter arouses mistrust among the prisoners, because it could well have been introduced by the enemy.

In Central Europe, resistance to the Germans in growing. But the partisan leader is denounced and killed. His daughter and the son of the traitor love each other. Condemned by his comrades, the informer commits suicide in front of the young couple.

In a film studio, several actors are the victims of attempted murders. Julien Brisseau, a writer, decides to use these facts as the backbone of his new novel. But while he is working on his detective story, young actors are actually killed. Julien thence gets suspected by police inspector Vétillard. To clear his name, Julien undertakes to investigate and find the killer on his own.

Hélène, a young waitress working in a bar frequented by German soldiers, saves the life of Pierre, a Resistance fighter. Her jealous lover has her arrested first and then released. Later on, Hélène is wounded while walking in the streets. Pierre has her transported to friends with the hope of taking her to London with him. Unfortunately, owing to lack of space in the plane, Pierre has to fly alone. Hélène has to wait several weeks before being able to board a new plane. When the day comes at last, the Germans are waiting for the plane on the clandestine airfield.