Marius and Cosette continue to live married life without Valjean in the picture. Marius even takes Cosette to visit his father's grave and he tells her the whole story of his father's tragic life.
Meanwhile, Valjean becomes so lonely without Cosette that he stops eating and grows sickly. A doctor visits and says that the situation looks no bueno.
One day, Valjean cracks. He gets himself a pen and paper and starts writing a letter to Cosette. In this letter, he explains how he made his fortune by perfectly legal means and that Cosette and Marius shouldn't be afraid to enjoy it with a clear conscience.
Once he's done this, he finds he can no longer lift his pen, and he collapses, knowing that he'll never see Cosette again.
While this is happening, Marius receives a different letter at his house. The writer of the letter claims to have valuable info about Cosette's father. It's basically a letter of blackmail, and surprise surprise, it's signed by Thénardier, who just happens to be waiting downstairs.
Marius heads downstairs to speak with Thénardier. But Thénardier is in for an unpleasant surprise. Marius already knows the whole story of Jean Valjean, and Thénardier has nothing to blackmail him with.
It turns out that Thénardier wants money so he can move to the New World (Central America, to be more specific) and start a new business.
While they speak, Thénardier claims that Valjean is a murderer, and Marius says that he already knows that Valjean murdered Inspector Javert.
Never one to stick to a plan that's not working out, Thénardier changes tactics and tells Marius that Javert committed suicide. He even has a newspaper article to prove it. He also shows an article explaining how Valjean made all of his fortune honestly as a businessman.
On the subject of murder, Thénardier says that he saw Valjean carrying a dead body out of the Paris sewer one day, and he produces the fabric he tore off Marius' coat as proof.
All he ends up doing, though, is confirming for Marius that Jean Valjean saved his life. Marius is bowled over. Out of respect for his father, he gives Thénardier enough money to move to Central America, then heads out in search of Jean Valjean.
Back at the Valjean house, Valjean hears a knock on the door and Cosette and Marius come pouring into the room. They quickly explain to Valjean that they understand his story completely and love him more than ever.
It's too late to save Valjean's life, though. In one last tender moment, he, Cosette, and Marius say their goodbyes. Valjean tells the young lovers to be good people and to live life to its fullest. Then he dies.
Jean Valjean ends up buried in an unmarked grave. It looks like the guy was humble to the end. But despite his efforts to die anonymously, someone uses chalk to scribble a poem on his blank gravestone.
In the passing years, these words have disappeared, but at one point, there was a poem about how people live and die and the cycle of nature goes on.
Okay, it's a bit cliché, but how else could you sum up a book this huge?