After they lose the inn in bankruptcy, they change their name to Jondrette and live by begging and petty thievery.

The novel portrays them as shameless and abusive figures; some adaptations transform them into buffoonish characters, though sometimes still criminals, to provide comic relief from the generally more serious tone of the story.

When Hugo introduces the Thénardiers, they have two daughters named Éponine and Azelma, whom they spoil and pamper as children, and a son called Gavroche.

[2] Fantine, a struggling single mother, arranges for her daughter Cosette to stay with them, if she pays a regular fee.

The Thénardiers treat Cosette quite poorly, dressing her in rags, selling her clothes for 60 francs in the streets of Paris, forcing her to work, and beating her often.

He finds Cosette all alone fetching a pail of water for the Thénardiers in a dark forest and accompanies her back to the inn.

After arranging lodgings at the inn for the night, he observes how the Thénardiers abuse her and how Éponine and Azelma mimic their parents' behavior and complain when Cosette plays with their doll.

The inn, which is forced to close down after Cosette is taken, is called "The Sergeant at Waterloo", because of a peculiar adventure that M. Thénardier had following the famous battle.

While looting the corpses shortly after the fighting had ceased, M. Thénardier accidentally saved the life of a Colonel, The Baron Pontmercy.

The tale as told by Thénardier eventually transformed into one of him rescuing a General during the heat of battle under a hail of grapeshot, as it grew more elaborate with each telling.

In a bizarre coincidence, the Thénardier family ends up living next to the disgraced son of the baron, Marius Pontmercy, at an apartment building named Gorbeau House nine years after the closing of the inn.

Marius, observing the Jondrettes through a crack in the wall, recognizes Cosette as the girl he met in the Luxembourg Garden.

When Valjean returns with rent money, M. Jondrette and Patron-Minette ambush him and he reveals his real identity: M. Thénardier.

Marius, torn between his desire to aid Valjean and his sense of duty to the man who had once saved his father, does not signal the police.

Marius remembers that Éponine had come into his apartment earlier and wrote on a sheet of paper "The cognes (police) are here" to prove her literacy.

Gavroche, not involved with his family's crimes, encounters purely by chance his two younger brothers, who are unaware of their identities.

M. Thénardier and Patron-Minette, with the aid of Gavroche, manage to escape from jail and attempt to rob Valjean's house.

Both Éponine and Gavroche are killed at Rue de la Chanvrerie, despite Marius' efforts to protect the Thénardier family.

He tells Thénardier he knows enough of his criminal past "to send you to the galleys", gives him 1500 francs, and orders him to leave and never return.

They welcome all customers to their inn, but whilst they appear to look friendly and welcoming, they secretly con their customers with watered-down wine, sausages made with horse kidney or cat liver, and extra fees for ridiculous things such as lice, looking in their mirrors, and keeping their windows closed.

Valjean tells them of Fantine's death and initially requests to take Cosette with him, but the Thénardiers attempt to con Valjean, falsely claiming they love Cosette as if she was their own daughter, have had to purchase expensive medicine to treat her for frequent illness, and are worried about the treacherous people she may encounter in the outside world ("The Thénardier Waltz of Treachery").

In the end, Valjean offers 1500 francs to take Cosette, and, delighted with the money, the Thénardiers hand her over without question.

With the help of robbers Brujon, Babet, Montparnasse, and Claquesous, they surround Valjean and rip open his shirt, revealing the brand on his chest.

Thénardier and his gang of robbers reach the gates of Valjean's house on Rue Plumet, when Éponine intercepts them and tries to force them to leave in order to protect Marius.

Along with Javert, they do not appear in the show's finale, presumably due to their villainous roles, as well as the fact that they are among the few characters to survive the entire play.