Mathilde Loisel initially refuses to go to the ball hosted by her husband's boss, who is the Minister of Public Instruction, until her husband buys her an expensive new dress and she finds a valuable piece of jewelry to wear. Fortunately, Mathilde's husband concedes and ends up buying her a beautiful dress. Mathilde then borrows a seemingly expensive diamond necklace from Madame Forestier and attends the magnificent ball.

After thoroughly enjoying herself at the ball, Mathilde Loisel and her husband hail a cab and travel home. Once they arrive home, Mathilde begins removing the wraps around her shoulders in front of a mirror when she discovers that the diamond necklace is not around her neck. After frantically checking all of their pockets and the folds in her dress, Mathilde's husband heads back outside to retrace their steps but does not find the diamond necklace. Mathilde and her husband end up buying a similar authentic necklace to return to Madame Forestier and spend the next ten years of their life making financial sacrifices to pay off the debts incurred from purchasing the expensive piece of jewelry. Ironically, Mathilde discovers that the necklace she lost was simply a worthless imitation.

Madame Loisel has a most successful evening, dancing the night away while her husband dozes in a corner. When it is time to go home, Monsieur Loisel gathers up some of her everyday things to cover her when they go outside, since it is cold.  She does not want anyone to see her in these clothes, since they are not as nice or as fancy as she would like, so she hurries out, and then the couple cannot find a taxi. Eventually, they find a humble carriage, which deposits them at home.  When Madame Loisel pauses to admire herself in front of the mirror, reliving her glorious evening, she realizes the necklace is missing.  They search everywhere in the house, and then Monsieur Loisel goes out to try to retrace their steps, but he comes home in failure.  Thus, Madame Loisel's actions, her haste, her unwillingness to live happily within her means, and her dishonesty set the stage for many years of hard work and grinding poverty.