The chapter opens with an estate auction. The narrator muses about how quickly life can change – one day a guy is rich, and the next all of his belongings are for sale to random strangers.
In any case, the next item up for auction is a portrait of a fat guy on an elephant. The painting is heckled and mocked, and finally a young couple (obviously Becky and Rawdon) buy it for a ridiculously low price.
The next auction item is a small piano. The young couple tries to buy it, but it is bought instead by a tall, gangly, awkward army officer (obviously Dobbin).
So what's going on? Well, the auction is selling off the property and household goods of the Sedleys. Mr. Sedley has gone bankrupt and has been kicked off the Stock Exchange. The Sedleys have had to move to a tiny house in a very low-rent part of London.
At the auction, some people bought things to give back to the Sedleys. The piano, for instance, was bought by Captain Dobbin, to return to Amelia.
Meanwhile, it's been a month since Becky left Miss Crawley's house. Miss Crawley still refuses to see Becky or Rawdon, and Mrs. Bute is still there. But so far, married life is nice for them, and Becky still puts on the full charm offensive.
The marriage is still secret and has not been published in the paper (which is what would normally happen when an aristocrat like Rawdon got married). The reason? Becky is worried that if all the people to whom Rawdon owes money find out that he has married a poor girl, they won't give him any more credit. And if they don't give him credit, there'll be nothing at all for them to live on.
The narrator does a little aside, explaining that manly, self-confident, aristocratic guys like Rawdon have figured out a way to live basically for free. They get credit on the strength of their family name and the expectation that when someone dies they'll get a big inheritance.