When Mme. Forester reveals that the necklace was a fake, the reader feels the force of irony Explain what makes the story’s closing sentence ironic.

In the last sentence of "The Necklace," Madame Forestier reveals that the jewelry that Mathilde had lost was, unbeknownst to her, completely worthless. The irony here is twofold. First of all, Madame Forestier's shock revelation shows that Mathilde and her husband have been slaving away all these years to pay off the debts they incurred in buying an expensive replacement necklace. Yet the necklace which they bought now turns out to have been a replacement for a fake. All that hard work, all that toil, and all that sacrifice has been for nothing.
Secondly, Mathilde wore the necklace to the Education Ministry ball as she thought it would give her the appearance of being richer and more socially prominent than she actually was. Yet now, thanks to years of financial struggle and hardship, Mathilde occupies a very lowly position on the social ladder. She thought that wearing the necklace would be her entree into high society. But instead it's led to her ending up at the very bottom of the heap.