Mrs. Danglars and her boy-toy Debray are about to go to bed when Mr. Danglars kicks Debray out of her room and has a word with his wife.
Mr. Danglars tells Mrs. Danglars that he knows Debray gives her inside information on the stock market and on government matters. He knows that Debray has helped her make money off of the stock market and that he has kept a lot of the money they have made. But, Danglars is super mad that Debray caused them to lose nearly one million francs when a false news report of a revolution in Spain broke out.
What's more, Danglars tells his wife that he knows about all of the lovers she's had in her day. He knows that she had a child by Villefort at one point.