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 ...