The main characters Madame and Monsieur Loisel live in an apartment in France around the 1800's. They are around middle class status.
Madame Loisel is middle class with her husband, but she desperately wants a life of wealth and a husband who loves her but is rich.
Monsieur Loisel gets an invitation to a party from his work as a minor clerk. Madame Loisel complains that she does not have anything to wear, nor any jewelry, so Monsieur Loisel lets her buy a dress for 400 francs. She also borrows a necklace from her friend, Madame Forestier.
Ha! After all those years you didn't notice that it was different because we lost it!
When Madame and Monsieur Loisel get home from the party, Madame Loisel realizes that the necklace was gone. But the Loisels keep it quiet, not telling Madame Forestier.
Monsieur Loisel tries finding the necklace, but to no such luck. He gets loans from some bad people on the streets, and uses his 18,000 francs of inheritance to buy a new necklace to replace the lost one. The Loisels end up paying everything back over the next ten years.
Madame Loisel ends up running into Madame Forestier while taking a walk, and decides to tell her the truth of what had happened, thinking that it would ruin her or confuse her. But, instead, Madame Forestier looks at her and tells her that the necklace that she let her borrow was a fake and only costed 500 francs.