First, we learn that the Crofts are in Bath - Mary has sent a letter along with them, and they've had it sent 'round to Anne Elliot. A word about this practice, and about the mail in Regency England:
Often you'll hear that letters were expensive during that time period, which is both right and wrong. If one were a member of Parliament, one would "frank" their letters and they'd be delivered for free. Often, MPs franked mail for everyone in their household and other people in their neighborhood. If that were the case, then one could send as many pages as one wished.
One did not pay to send a letter through the postal service. One paid to receive a letter. How much one owed to receive a letter depended on two things: how thick it was, and how far it had come. Letters were sent without envelopes, but were folded up and sealed with wax, thereby limiting the amount of a piece of paper on which one could write. Mary's letters to Anne were probably of moderate length - one page, two at most - because to do otherwise might pose an imposition on the recipient, who is responsible for payment. Imagine paying for a letter to find only one or two sentences - what a ripoff! - or paying the exorbitant rate for a multi-page packet only to find that the outside sheet was completely blank. What sort of person would be so inconsiderate? Not Mary Musgrove, in any case.
Mary has sent her letter along with the Crofts, who have agreed to carry the letter with them to Bath. This allows Mary to engage in a longer, chattier letter than she might otherwise have sent if Anne had to pay for it.
I love Mary's letter - how she's snitty with everyone in the first installment (when she feels overlooked) and very happy with them once she feels she's been paid her due. I especially love her initial post-script:
"I am sorry to say that I am very far from well; and Jemima has just told me that the butcher says there is a bad sore-throat very much about. I dare say I shall catch it; and my sore-throats, you know, are always worse than anybody's."
The second part of Mary's letter is far more interesting, and leaves Anne completely gobsmacked. It turns out that Louisa is engaged to marry Captain Benwick. Anne never saw it coming, although some readers aren't entirely shocked, recalling that Benwick stayed in Lyme while Wentworth effed off to Somerset. Kinda makes one wonder whether we'll be seeing Wentworth again soon, doesn't it? (We will. We definitely will!)
Here's Anne's take on Benwick and Louisa, and once again, she appears to see things quite clearly:
She was persuaded that any tolerably pleasing young woman who had listened and seemed to feel for him would have received the same compliment. He had an affectionate heart. He must love somebody.
She saw no reason against their being happy. Louisa had fine naval fervour to begin with, and they would soon grow more alike. He would gain cheerfulness, and she would learn to be an enthusiast for Scott and Lord Byron; nay, that was probably learnt already; of course they had fallen in love over poetry. The idea of Louisa Musgrove turned into a person of literary taste, and sentimental reflection was amusing, but she had no doubt of its being so.
Anne is keen to see the Crofts, of whom she has become fond, and is pleased to see them walking about town together:
Knowing their feelings as she did, it was a most attractive picture of happiness to her. She always watched them as long as she could, delighted to fancy she understood what they might be talking of, as they walked along in happy independence, or equally delighted to see the Admiral's hearty shake of the hand when he encountered an old friend, and observe their eagerness of conversation when occasionally forming into a little knot of the navy, Mrs. Croft looking as intelligent and keen as any of the officers around her.
Oh Anne - thinking of what might have been. And no doubt hoping it might be again, given the news of Louisa Musgrove's engagement to Captain Benwick. Then one day, Anne runs into the Admiral and walks up the hill with him, and we are treated to a quite amusing conversation (I love the Admiral, as does Anne, I think), in which he speaks of the situation between Louisa and Benwick and also tells Anne that Wentworth seems perfectly blasé about the entire thing. The chapter ends with the Admiral telling Anne that he and his wife really ought to ask Captain Wentworth to come to Bath, oughtn't they?