The heroine in L'Eau Vive is the unwilling heir to a fortune. Young Hortense (Pascale Audret) has always known that her family was greedy, but until she inherits her father's hidden millions she has no idea how loathsome her relatives could be. Surrounded on all sides by grubby, outstretched hands, Hortense takes some comfort in the fact that her legacy is still missing. When the money is finally recovered, our heroine does the "right thing" with her windfall, leaving her mercenary family empty-handed. Throughout the film, Hortense's dilemma is likened to a government dam project not far from her home; as the bridge grows in size, so too does Hortense's resolve to rise above the nastiness all around her.

In a settlement in the northern mining country. The Marles, Bréhard and Gohelle families wake up and prepare for a new day at work. The young engineer Larzac, newly appointed to the mine, will soon oppose the authoritarian and conservative methods of his superior Dubard. Georges Gohelle would like to marry Marie Bréhard, but housing difficulties thwart their plans. Brezza, a Polish immigrant, who must return to his country, would like to hate his marriage to Louise Gohelle. Roger, Marie's little brother, has just turned 14. He does not want to go down to the mine as his elders have always done. He will however have to resign himself to it. Marles evokes for him the social struggles of 1906. Roger is injured during a landslide. In front of his family and his friend Marles, who had come to the hospital, he announced his decision to continue his profession. Larzac, invited to the Marles, reveals that he refused a quiet position at the Charbonnages de Paris. He too stays.