Victor Valance, an absent father and gambler, works with shady casino operations abroad. When he returns to Paris in need of money, he plans to take advantage that Pauline, his eldest daughter now fully responsible for the whole family, has begun to work for the Ministry of Finance. Pauline thwarts his new projects but when she realizes gangsters are looking for Victor she will put her life at risk to help him and save their family.

A spy is given an important mission: to shed light on the mysterious Bactron 317.