The book follows her as she tries unsuccessfully to marry Percy Gryce. Trenor, who was helping match Lily and Mr. Gryce, is furious with the way Lily ruined her chances with him. Lily accepts the rebuke and goes to pick up Mr. Trenor from the train station. On the way home she asks him for money, and he agrees to "invest" on her behalf. She soon receives a check for one thousand.
Mr. Trenor is a wealthy family man who loans Lily money but expects sexual favors in return. She rejects his advances and makes Mr. Trenor mad; but he never harms her. .
The material wealth in The House of Mirth is shown through this main storyline. Mr. Trenor uses his money to try to have sexual relations with Lily. Lily's actions after being rejected from both men, Mr. Trenor and Selan, are devastating. She is no longer seen as a "young woman in the upper-class New York society." Her interest in money is lost. Lily runs into a woman whom she once gave charity money to and is asked to come to her house and warm up. After Lily returns to her boarding house, she lays out her dresses and looks at them, remembering all the occasions she used them. Her maid hands her a letting containing the ten thousand dollar check with her inheritance. She writes a check to Mr. Trenor to pay off her debts, and then overdoses on choral, a sleeping tablet. .
Selan goes to Lily's house to clear things up between the two of them. He enters her room to find her lying motionless on the bed. He also sees the note to Trenor and the checkbook balance, and realizes that Lily had been in debt to Trenor. Selden is left at the end not knowing what Lily had really been doing with Trenor, but blaming life for having kept them apart. .
The House of Mirth can be compared to The Rise of Silas Lapham in terms of material wealth and class level in society. Both storylines have high class people in a society who are interest only in money. In the Rise of Silas Lapham, Roger, who was a one-time partner gains advantage over Lapham through blackmail.