In this story, we are introduced to Matilde Loisel. Since she was a child, Matilde wanted to live a life full of riches and glamour; however, she has lived her whole life impoverished. It's because of this that she finally marries a man who is a minor civil servant at the Ministry of Education.
One day after work, Monsieur Loisel comes home with an envelope. Once he hands it to Matilde, she immediately opens it up to find it is an invitation to a party; however, rather than be excited, she seems more upset. She explains on pg. 285, "I haven't got a thing to wear. How could I go?"
As Matilde begins getting ready for the ball, she notices she has nothing shiny to present. This is where we meet Matilde's friend, Madame Forestier. Matilde asks Forestier if she can wear her diamond necklace, which she gladly obliges to as long as Matilde will return it.
After the party has ended, Matilde notices now that the necklace she was once wearing has now disappeared. This sends her into a fury of shock and confusion as she and her husband search for the diamond necklace. Sadly, the search is unsuccessful and they do not find the necklace.
After Matilde has lost the necklace, she formulates a plan where they will buy another necklace to act as a replacement. Though the idea works, they've used up so much money that now they are impoverished and must work hard labor, which they do for the next 10 years.
While Matilde is at a market, she happens upon who she realizes is Madame Forestier. When Matilde tells Forestier that the necklace she bought was real and costed her so much that she went bankrupt, Forestier tells her that the necklace was fake and that "it was worth five hundred francs at the most".