Mr. Bennet had never saved money, assuming that he would eventually have a son who would then inherit the family estate.
Bad assumption. Instead, they had girl after girl after girl after girl after girl, at which point it was too late to start saving for the girls' future.
He writes a letter of thanks to his brother-in-law, Mr. Gardner, for essentially bribing Wickham into marrying Lydia and promising to pay him back.
Mrs. Bennet discusses the wedding plans, but Mr. Bennet says he will not give his daughter even the tiniest amount of money for wedding clothing, and he refuses to receive the couple at Longbourn.
Historical Context Lesson: "Receiving" someone is similar to diplomatic recognition. If no one receives you, you basically don't exist in their eyes.
Elizabeth begins to wish she had never told Mr. Darcy about the Lydia-Wickham situation, since everything is turning out okay, now.
In fact, she's starting to realize that Mr. Darcy is pretty much perfect for her.
Mr. Gardiner writes that Mr. Bennet should never mention the debt again. He also says that Wickham has been convinced to leave his regiment and joins the Regulars (another variety of military service) so he won't be settling nearby—a relief to everyone except Mrs. Bennet.
Eventually, the sisters convince Mr. Bennet to let Lydia come for a visit.