As spring blossoms, so does the love between Marius and Cosette. Their bliss is almost dreamlike, but Valjean shatters their happiness when he announces that he plans to take Cosette to England in a week’s time. Valjean is quite sure that their house is being watched and has seen Thénardier loitering around the neighborhood. Just as Valjean suspects, Thénardier is indeed plotting revenge and robbery, but Eponine manages to delay her father’s plans. Valjean’s desire to leave Paris is clearly motivated by a fear of losing Cosette, but it also stems from his unease about the deteriorating political stability in France.
When Cosette tells Marius about Valjean’s plan, he is heartbroken. He goes to see Gillenormand, and although they have not yet reconciled, Marius begs his grandfather to grant him permission to marry Cosette. As they talk, Marius and Gillenormand begin to repair their relationship, but Gillenormand then makes the unfortunate suggestion that Marius make Cosette his mistress rather than marry her. Marius explodes, screaming that his grandfather has insulted his future wife and storms out of the house.
Marius returns to the house in Saint-Germain to see Cosette. When she fails to appear at the appointed time, Marius realizes that Cosette and Valjean have moved. Heartbroken, he has no time to grieve, since a mysterious voice advises him to join his friends on the barricades.
Paris is in the throes of a cholera epidemic, and the climate is so unstable that the slightest spark threatens to set off an insurrection. The spark finally comes on June 5, 1832, during the funeral procession of General Lamarque, a popular defender of liberty and the people. Fearing that the public mourning might lead to violence, the monarchy dispatches troops throughout Paris to maintain control. When shots are fired on the Austerlitz Bridge, the city explodes and barricades begin to spring up.
Marius’s former law-school companions, the Friends of the ABC, are among the first to answer the cries of revolution. The group begins to arm and prepare for the imminent confrontation with the army. Gavroche joins their ranks. As the mob marches through the streets, the old churchwarden Mabeuf joins them, following them doggedly even after they tell him to go home.
The students decide to build a barricade around one of their favorite meeting spots, the Corinth wine-shop. Gavroche is instrumental in building the barricade and organizing its defense. The revolutionaries build barricades from everyday items, and they are in high spirits as night falls. Gavroche tries in vain to persuade the men to give him a gun. When the construction of the barricades is done, the men sit and wait. Gavroche suddenly realizes that an unnamed man who has joined the group is actually Javert, who is spying on them for the army. The men take Javert prisoner. One drunken revolutionary shoots a local homeowner, and Enjolras executes the man on the spot. Enjolras delivers a rousing speech. Marius’s roommate, Courfeyrac, notices that a slim, young laborer who came looking for Marius earlier in the day has joined the group at the barricades.