The younger girls are despondent because the military regiment (i.e., the attractive men) will be leaving soon. The wife of the regiment's colonel invites Lydia to go to Brighton with them, though.
Elizabeth advises her father not to let Lydia go, pointing out the likelihood of Lydia's impropriety and imprudence.
Mr. Bennet is inclined to let the youngest Bennet girl go, saying any follies Lydia might commit in Brighton will be less likely to embarrass them locally.
Elizabeth says that Lydia's wildness already shames the entire family and hurts their reputation (she's thinking of how Darcy views the Bennet family).
She speaks with passion and her father recognizes it, but he says that Jane and Elizabeth's reputations cannot possibly be hurt by their three very silly sisters.
Lydia would have been furious if she had known that Elizabeth was trying to deny her the joy of flirting with untold numbers of men.
Elizabeth can now finally say goodbye to Wickham. She has seen plenty of him and now abhors parts of his personality which before seemed delightful.
When she has a chance, she informs Wickham that she spent three weeks in the company of Mr. Darcy and Colonel Fitzwilliam. She lets Wickham know that she liked the colonel immensely, and adds that Mr. Darcy's personality and manners improve as she gets to know him better.
Wickham is alarmed and agitated. He tries to engage Elizabeth in abusing Mr. Darcy, as they used to do, but Elizabeth just smiles.
When the party is over, Lydia goes with her friend to Meryton; in the morning, they will leave for Brighton.