What does Walton’s frame narrative do?

Robert Walton’s letters make Frankenstein a story about listeners, not only about a monster. Walton is already risking his crew for glory in the Arctic when he takes the dying Victor aboard. Victor’s confession is meant as a warning, and the continuation shows Walton choosing — under pressure from his sailors and from what he has heard — not to repeat the whole pursuit.

The frame also keeps Victor from owning the book. We receive his self-portrait through an admirer who is disposed to find him noble, then we receive the creature’s rebuttal inside that portrait, then Walton’s last view of both. Ambition stays attractive; that is why the warning can fail. Without the letters, the novel would be a private melodrama. With them, dangerous knowledge is a temptation offered to the reader in the same ice where the story ends.