Final answer:
The reader realizes all of Désirée's hope is in vain and that this story is leading to a dark conclusion when the narrator explicitly states his lesson learned and adds a detail about his continuing humiliation.
Step-by-step explanation:
The sentence where the reader realizes all of Désirée's hope is in vain and that this story is leading to a dark conclusion is: "Resolution. The narrator explicitly states his lesson learned at the end of the story and adds a detail about his continuing humiliation." This sentence indicates that the story will end in a tragic manner and that Désirée's hope will not be fulfilled. It sets a dark tone and foreshadows a negative outcome.