He has bought himself everything Society requires: a wife with a huge rack for jewelry display, a stepson who is dumb but popular, a fancy mansion, and the world's most impressive butler.
Merdle throws fancy dinner parties, which he barely attends and doesn't seem to enjoy very much.
His guests brag and argue over how much money he has made, and when he finally shows up, they hit him up for donations or investments.
The last guest at the Merdle shindig is Physician. It seems Mr. Merdle thinks there's something wrong with him and has been going to see the doctor. The doctor can't figure out what, if anything, is the matter.
The other guests think maybe it's stress-related.
The narrator hints that we'll see what's wrong with Merdle soon enough.