Although Austen makes reference throughout the novel to letters sent from one character to another, Chapter 29 is exceptional because it includes the full text of four letters sent between Willoughby and Marianne. Chapter 29 perhaps most closely resembles Austen's original 1795 manuscript for the book, which was conceived as an epistolary novel entitled Elinor and Marianne. It wasn't until at least four years later that Austen rewrote these letters with narration.
Elinor feels that Willoughby's letter proclaims him to be "deep in hardened villainy." Indeed, Willoughby is only one in a long line of Austen's male villains, including George Wickham (of Pride and Prejudice), Henry Crawford (of Mansfield Park, and Frank Churchill (ofEmma). All of Austen's villains are tricksters, who initially seem charming, attractive, and witty. Some, like Frank Churchill, turn out to be fibbers and play-actors while others, like George Wickham, are downright frauds. However, Willoughby is both: he is a glamorous seducer as well as a corrupt philanderer. He is not just impetuous but also callous; he is not just insensitive but also vicious. As a result, it is not difficult to see how he can capture Marianne's heart without ever fully winning Elinor's confidence.
The contrast between Elinor and Marianne is perhaps made most explicit in their reactions to their lovers' seemingly insensitive treatment. Whereas Elinor is relieved that she does not have to share Lucy's news about Edward with her mother and sister, Marianne insists through her grief that "I care not who knows that I am wretched." Her attempt to claim intimacy with Willoughby at the party dramatizes the dangers of showing one's feelings publicly and contrasts strikingly with Elinor's more cautious restraint.
Colonel Brandon's own personal story of his relationship with Eliza Williams and her daughter elaborately echoes Marianne's relationship with Willoughby. The details of Brandon's story parallel all of the plots of the novel, including that of the insensitive parent's commitment to primogeniture, of brothers who cannot see eye-to-eye, and of women whose hearts are broken by the men they love. However, Brandon's dramatic story also includes divorce, seduction, illegitimate birth, and even a duel, all of which are extreme consequences of the emotions and situations that Marianne Dashwood must confront. Though Brandon comments that he is a "very awkward narrator," his story-within-a-story actually sheds light on many of the most important themes of the novel.