Eponine is the oldest daughter of Monsieur and Madame Thénardier, a pair of innkeepers with a penchant for swindling their guests out of money. During her early childhood, Eponine and her younger sister, Azelma, are spoiled by their parents, but once their parents' innkeeping business falls apart, the whole lot of them are forced into poverty.

At first, Eponine seems like she will turn out no differently from her materialistic and conniving parents. As a child, she joins in on the mistreatment of Cosette, a young girl her own age whom the Thénardiers regard as little more than a slave, to the point that she resents the love-starved girl playing with one of her discarded dolls. In her adolescence, she aids her parents in their criminal schemes.

However, the humbled teenage Eponine displays flashes of morality which complicate her character. She further becomes redeemed through her unrequited love for Marius Pontmercy. While her parents are supremely selfish, Eponine dies taking a bullet for Marius, the ultimate selfless act. This love enables Eponine to escape becoming like her mother and father and allows her to evolve from a minor antagonistic force in her early appearances to one of the novel's most noble characters.