Mathilde is a story about a young woman who marries a wealthy man named Loisel. Despite their comfortable lifestyle, Mathilde is unhappy because she longs for a life of luxury and glamour. One day, she borrows a diamond necklace from a friend to wear to a fancy party, but loses it on her way home.
Instead of telling her friend the truth, Mathilde and Loisel go into debt to buy a replacement necklace. They spend years working to pay off the debt, living in poverty and struggling to make ends meet. It's not until after they have paid off the debt that Mathilde learns the necklace she lost was actually a fake.
The story serves as a cautionary tale about the dangers of vanity and the consequences of dishonesty. Mathilde's desire for material wealth leads to her downfall, and she ultimately realizes that true happiness cannot be found in material possessions.