Jean Valjean, a man sentenced to 19 years of prison for stealing a loaf of bread, is released on parole but is rejected by society due to his criminal past. He finds refuge with Bishop Myriel, who treats him with kindness. Valjean, out of desperation, steals the bishop’s silver but is caught. Instead of condemning him, the bishop gives him the silver and encourages him to become an honest man. Deeply moved, Valjean breaks his parole and reinvents himself as Monsieur Madeleine, a wealthy factory owner and mayor of Montreuil-sur-Mer. However, Inspector Javert, a strict enforcer of the law, suspects his true identity.

Meanwhile, Fantine, a young woman abandoned by her lover, struggles to provide for her daughter, Cosette, who is left in the care of the cruel Thénardiers. When Fantine is dismissed from her job unfairly, she falls into poverty and turns to prostitution. She is eventually arrested by Javert, but Valjean intervenes, taking her under his care. Before dying, Fantine entrusts Cosette’s future to Valjean. When Javert learns Valjean's true identity, he pursues him. Valjean escapes and rescues Cosette from the Thénardiers, raising her as his daughter.

Years later, in Paris, Cosette and Marius, a young revolutionary, fall in love. Marius is part of a group of student revolutionaries planning an uprising against the monarchy. Valjean, fearing for Cosette's safety, tries to separate them, but Marius remains committed to his cause. During the June Rebellion of 1832, the revolutionaries build barricades, but their efforts are doomed. Valjean, despite his past, saves Marius's life by carrying him through the Paris sewers after the massacre.

Javert, captured by the revolutionaries, is given to Valjean for execution, but Valjean spares his life. This act of mercy shatters Javert’s rigid worldview, leading him to take his own life. Marius, unaware of Valjean’s sacrifice, recovers and marries Cosette. However, when Valjean confesses his past, Marius shuns him, believing him to be a criminal. Later, after learning the truth about Valjean’s heroism, Marius rushes to reconcile, but Valjean is already dying. In his final moments, Valjean dies peacefully, having found redemption and love.

The novel concludes with Valjean's epitaph, marking the journey of a man who transformed from a despised ex-convict into a figure of selflessness and love, highlighting Hugo’s message of justice, mercy, and human dignity.