Madame Loisel gets an invite to a party in which her husband had gave her. She got money from her husband to buy a dress and she even borrowed a necklace from one her her friends who had a good amount of wealth.
Madame Loisel goes to the party. When she was on her way home she had lost the necklace. Her and her husband had tried to retrace their steps but they could not find the necklace which was so beautiful.
Her husband had went to many jewelers to find a necklace that looked similar to the one in which that Madame Loisel had borrowed from her friend. They buy the necklace.
Madame Loisel and her husband returned the necklace to the friend from whom she had borrowed Madame Loisel had borrowed the necklace from.
The Loisels do many years of work in order to make up all the money that was promised in order to be able to replace that necklace that was lost. Madame Loisel had to fire her maid and start doing that house work at the house. She aged poorly.
Madame Loisel had spotted her friend who had let her borrow the necklace. Even tho she may not have recognized her Madame Loisel went up tho her to tell her about the problem that she went through in order to make enough money for the necklace. After all those years of work, her friend tells her the the precious "Diamond" necklace was actually made out of paste which only look like precious gems.