monsieur loisel gets his wife an invitation to a party but does not want to go since she has nothing nice to wear
madame loisel gets a new dress and barrows a necklace from Forestier
madame loisel goes to the dance with her husband and they lose the necklace
they try to retrace all of their steps, and they tell Forestier that the clasp broke and they are getting it fixed so that they have more time to find it. They pull out loans from loan sharks and live with 10 years or debt.
they go and buy a new necklace and worth 45,000 franks and they tell Forestier about the whole thing and they learn that the necklace was a fake and only worth 450 franks