Jean Valjean, released after nineteen years in the galleys, is taken in by Bishop Myriel of Digne despite his yellow convict's passport. He steals the bishop's silver overnight. Arrested and brought back, he is astonished when the bishop covers for him, gives him the candlesticks as well, and insists the silver was a gift. Valjean then steals a coin from a chimney sweep by reflex — and is horrified by himself. The transformation begins.

Eight years later: Valjean is Monsieur Madeleine, factory owner and mayor of Montreuil-sur-Mer. Fantine, a factory worker, is dismissed when her illegitimate daughter is discovered. She descends from worker to prostitute to prisoner, selling her hair, teeth, and body to pay the Thénardiers for Cosette's upkeep. Javert arrives as police inspector and recognizes something in Madeleine. Valjean intercedes to save Fantine from prison and promises to find Cosette.

Javert reports that 'Jean Valjean' has been captured — an innocent vagrant named Champmathieu who matches the description. Valjean agonizes all night over whether to let an innocent man be condemned in his place. He goes to Arras, announces himself in open court, and is recaptured. He escapes briefly to keep his promise to Fantine, returns to her deathbed, and is recaptured again. He later escapes once more at sea during a naval rescue and disappears.

Valjean retrieves Cosette from the Thénardiers in Montfermeil on Christmas Eve. He finds her fetching water in the dark, gives her a doll, and buys her freedom from the Thénardiers — who demand money but cannot legally hold her. He and Cosette flee to Paris, live briefly at the Gorbeau tenement, are traced by Javert, and escape into the convent of Petit-Picpus, where they live in hiding for years.

Marius Pontmercy, raised by his royalist grandfather Gillenormand after being separated from his Bonapartist father, discovers his father's history after the elder's death. He becomes a republican idealist and joins the Amis de l'ABC — a student revolutionary society including Enjolras, Courfeyrac, and Combeferre. He falls in love with Cosette across a bench in the Luxembourg Gardens. He is being watched by the Thénardier family, now living in poverty in Paris under the alias Jondrette.

Valjean and Cosette live peacefully at the Rue Plumet. Marius finds Cosette. They meet in the garden and fall in love properly. Valjean senses his displacement. The Thénardier gang plots robbery. Revolutionary tension builds in Paris — cholera, a funeral procession for the republican General Lamarque. Éponine intercepts a letter from the gang to Valjean, then confesses her love to Marius and leads him to the barricade rather than to Cosette.

The barricade on the Rue de la Chanvrerie rises and falls over two days. Enjolras leads the students. Javert is captured as a spy, bound, and handed to Valjean to execute — Valjean instead releases him. Éponine dies in Marius's arms delivering Cosette's letter. Gavroche, the street urchin, is killed gathering cartridges outside the wall. Marius fights, is gravely wounded as the barricade falls. Valjean carries Marius through the Paris sewer system to safety.

Javert allows Valjean to deliver the wounded Marius to his grandfather's house. Alone on a bridge over the Seine, Javert confronts the impossibility of integrating what he has witnessed — that a criminal can be a saint, that mercy can be real, that his entire moral architecture is false. He cannot arrest Valjean and cannot not arrest him. He jumps into the Seine.

Marius recovers; he and Cosette marry. Valjean confesses his criminal past to Marius before the wedding, insisting Marius know who he is. Marius, horrified and protective of Cosette, gradually withdraws Valjean from their lives — first reducing his visits, then excluding him. Valjean, unable to see Cosette, begins to die of grief. He sits alone in his room with the bishop's candlesticks, his only remaining objects.

Marius learns the full truth — Thénardier reveals that the man who carried him through the sewer was Jean Valjean. Marius and Cosette rush to Valjean's side. He is dying. He tells Cosette her mother's name, gives her the bishop's candlesticks, and dies peacefully in their arms. His grave has no name — only the epitaph someone has written in the earth.