How does Shelley return to her frame story in chapter 24?
The outermost frame story in the novel is Captain Walton's, an explorer who has sailed to the Arctic in order to look for the Northwest Passage. He is writing letters back to his sister Mrs. Saville, who is home in England. The story which Walton's story frames is Victor Frankenstein's, and Victor's story is the frame for the creature's story. You might even consider the creature's story as a frame for the story of Safie, Felix DeLacey's beloved. Victor completes his own tale by warning Walton about his creature's eloquence and persuasiveness, telling the captain not to trust the creature no matter what. He asks Walton to kill the creature and promises that he will "direct the steel aright." At this point, the text reads, "Walton, in continuation"; we get a date, and then the captain writes again in his own words.
The remainder of the book is again written in letters to his sister Margaret in Enlgland. This is where he tells of Victor's decline in health, the mutiny of his own sailors, and the visit of the creature after Victor finally passes. He records in letters the creature's conversation and also his vow to kill himself. He says that Robert is the last of his kind to see the monster with his own eyes, that the creature will build a funeral pyre and lavish in the torture of the flames. So, he does not kill himself in the novel...it happens after the book has ended, but the creature has always been a "man" of his word.
The novel begins and ends with Robert Walton writing letters to his sister.