The revolutionaries are temporarily victorious, but their morale falls when they learn that the rest of the city has failed to join their uprising. The army prepares another attack on the barricade, prompting Enjolras to urge all revolutionaries who have wives and children to return to their families. Though the men refuse, Enjolras insists, and the group votes on which five men to send away. Enjolras, however, has only enough army uniforms for four men to slip out in disguise. Out of nowhere, Valjean appears and offers to give up his own uniform for the fifth man.
Valjean is a valiant fighter but makes a point of not killing any of the enemy. Enjolras expresses regret at taking lives, but he is willing to kill for his beliefs. When the revolutionaries run low on ammunition, Gavroche bravely scrambles over the barricade to gather ammunition from the bodies of dead army soldiers. He almost returns to the barricades unharmed, but at the last minute he is shot twice and dies. Realizing that the army is about to storm the barricade, Enjolras orders Javert’s execution, and Valjean eagerly volunteers. Once they are alone, however, Valjean tells Javert his address and sets him free. Valjean fires a shot in the air so the others will think that he has executed Javert. When he rejoins the group at the barricade, Marius looks at him with dread.
The revolutionaries can no longer stave off the attackers, so Enjolras orders a retreat. They fall back into the Corinth wine-shop. Marius is shot, but Valjean catches him as he falls and carries him off. When the troops enter the wine-shop, they find only Enjolras. He is executed as the army hunts down and kills the remaining revolutionaries. Valjean, with the unconscious Marius slung over his shoulders, searches for an escape. All exits are sealed and the troops are fast approaching. Luckily, Valjean discovers a sewer grate and carries Marius down into the sewers with him.
The narrator bemoans the fact that Paris spends huge sums collecting bird droppings for fertilizer while washing out all the human waste that could serve the same purpose. We learn that the Paris sewers were once nightmarish places and are told of the great flood in 1802, which covered large parts of the city with waste and filth. A man named Bruneseau began an extensive redesign of the sewers. The work was finished years later, after a cholera outbreak.
It is clear that Marius desperately needs a doctor. Valjean can barely see in the darkness of the filthy sewers, but his instincts guide him toward the river Seine, and he rushes ahead to bring Marius to safety. Avoiding police patrols and fighting fatigue and hunger, Valjean finally stumbles upon an exit. To his dismay, he finds that the gate is locked and cannot be forced open. Thénardier appears out of the darkness, demanding money in exchange for opening the gate. Thénardier does not recognize Valjean and assumes he is merely a criminal who has killed a wealthy man. Marius has no money, and Valjean is carrying only a paltry sum. Thénardier reluctantly takes the money and opens the gate. He also rips off a piece of Marius’s jacket so that he can later identify Valjean’s victim.
Valjean emerges on the banks of the Seine, but his freedom is short-lived. Javert, who has been chasing Thénardier, is waiting at the sewer entrance. Valjean is so covered in mud and slime that Javert does not recognize him, but Valjean turns himself in anyway. Valjean begs Javert to let him return Marius, who is dying, to his grandfather. Javert agrees and takes them to Gillenormand’s house. After Valjean and Javert drop off the wounded Marius at Gillenormand’s house, Valjean asks Javert for one more favor: he wants to see Cosette one last time. Again, Javert agrees to Valjean’s request. Valjean goes up the stairs to see his adopted daughter with a heavy heart, but when he looks out the window, he is surprised to see that Javert is gone.