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 (Ronet), 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 (Seberg) 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 movement is hindered by an informer and another man who pretends to help the resistance fighters but leads them to the Nazis and steals all their possessions.

Source : Wikipedia