The disgraced companion now keeps London lodgings and, after resistance, gives Darcy the clue that finds Wickham and Lydia.
After her dismissal from Miss Darcy's charge, Mrs. Younge takes a large house in Edward Street and supports herself by letting lodgings. Mr. Darcy knows she remains intimately acquainted with Mr. Wickham and seeks her out as soon as he begins his London search for Wickham and Lydia Bennet.
Mrs. Younge initially withholds the information, apparently unwilling to betray Wickham without inducement, though he had called on her at their first arrival in London and would have lodged there had she had room. After two or three days she gives Darcy the direction he needs. Her cooperation is a crucial, morally compromised link in the chain that makes Lydia's rescue possible.
The text gives no description of her age, face, hair, complexion, build, or clothing.
She is the reluctant keeper of Wickham's London trail and the source of Darcy's decisive lead.