Luc Froment, a reform-minded engineer, starts working at a steel mill in a small town. There he founds small groups of workers (and their families) under miserable conditions. Under the influence of Fourier's ideas, Froment tries to turn the mill into a workers' co-operative.

When an unscrupulous banker ruins his family, a young man swears to bring him to justice, so he adopts a new identity, the mysterious Judex, and ominously disguised and sunk into the muddy path of vengeance, punishes the crooks and protects the innocents. (Originally a twelve-part epic serial.)

Mimi, an orphan, is taken in by a drunken innkeeper and becomes a domestic. She meets Rudolphe, scion of a well-to-do family, who rescues her from the unwanted advances of a drunken hotel guest. They fall madly in love, but Rudolphe's uncle, M. Durandin, wants Rudolphe to marry a family friend, Madame de Rouvre, and writes Mimi a letter, telling her that she is ruining Rudolphe's life. Musette and Marcel, friends of Mimi, also try to break up the romance by introducing Mimi to other men, and Rudolphe becomes jealous and leaves her. Brokenhearted, Mimi declines in health and eventually throws herself into the river but is rescued and taken to the hospital. Realizing it is only a matter of time before she dies, she drags herself back to the room where she and Rudolphe were happiest. Rudolphe is there and she dies knowing that he loves her.