The colonel's frank walk with Elizabeth accidentally reveals Darcy's decisive role in separating Bingley from Jane.
Colonel Fitzwilliam meets Elizabeth on a walk in Rosings Park and joins her back toward Hunsford. Their playful discussion of a younger son's dependence leads to his admission that men in his position cannot freely marry without money. He also confirms that he and Mr. Darcy share guardianship of Miss Darcy, showing a responsible family role beneath his easy social manner.
When Elizabeth teasingly observes that Darcy takes prodigious care of Bingley, Fitzwilliam says he has reason to think Bingley indebted to Darcy. He then recalls Darcy's recent claim to have saved a friend from an imprudent marriage, while carefully insisting that he is merely guessing Bingley was meant. His information, offered without malice and without knowledge of Elizabeth's personal stake, convinces her that Darcy has separated Mr. Bingley and Jane Bennet. He sees her distress but does not grasp its source.
He is about thirty, not handsome, and in person and address most truly the gentleman. His hair, complexion, build, clothing, and military dress are not described.
He remains Elizabeth's agreeable confidant, but his casual disclosure becomes the immediate cause of her crisis with Darcy.