In The House of Mirth (1905), the story of Lily Bart begins with her visiting the apartment of Lawrence Selden, a man for whom she has romantic feelings, but, for the sake of a high social-standing, decides that she must marry Percy Gryce, a young, timid millionaire who is wealthier than Selden. Despite the people of her social circle being convinced that Percy will propose marriage to Lily when they next meet, Lily changes her mind, and withdraws from their relationship, on account of an unexpected visit from Lawrence Selden. Despite feeling convinced that he loves Lily, Selden does not yet want to risk marriage; meanwhile, Gryce marries another girl, from within their social circle.
Her social standing begins to erode when Gus Trenor, husband of friend Judy, gives Lily a large sum of money, accepted in the innocent belief that it represents profits from investments Gus had made in her behalf. The rumors that arise from that transaction, worsened by her injudicious and mysterious visit to Gus's townhouse in the city, further erode Lily's social standing. In the event, Lily one day receives a note from Selden, who asks to meet with her; certain that he shall propose marriage, Lily accepts to meet him the next day. Surprised by her acceptance, Selden becomes frightened by Lily's apparent change-of-heart, because earlier, Lily had escaped his attempt to kiss her; the fearful Selden flees New York City, first to Havana and then to Europe, cravenly leaving Lily with no notice.
To escape the rumors arisen from the gossip caused by her financial dealings with Gus Trenor, and also disappointed by Selden's emotional cowardice, Lily accepts Bertha Dorset's invitation to join her and her husband, George, on a cruise of Europe aboard their yacht, the Sabrina. Unfortunately, whilst at sea, Bertha falsely accuses Lily of adultery with George, in order to thwart the attention and suspicion of their social circle away from Bertha's infidelity with the poet Ned Silverton. The ensuing social scandal ruins the personal reputation of Lily Bart, which then causes her abandonment by friends and disinheritance by Aunt Peniston.
Undeterred by such misfortunes, Lily fights to regain her place in high society, by befriending Mr and Mrs Gormer, but her enemy, the malicious Bertha Dorset, gradually communicates to them the “scandalous” personal background of Lily Bart, and, so, undermines the friendship with the Gormers, by way of whose sponsorship Lily hoped to become socially rehabilitated. Only two friends remain for Lily: Gerty Farish (a cousin of Lawrence Selden) and Carry Fisher, who help her cope with the social ignominy of a degraded social-status, whilst continually advising Lily to marry as soon as reasonably possible.
Despite the efforts and advice of Gerty and Carry to help her overcome notoriety, Lily descends through the social strata of the high society of New York City. She obtains a job as personal secretary of Mrs. Hatch, who is a disreputable woman; and Lily resigns after Lawrence Selden returns to rescue her from complete infamy. Lily then finds a job in a milliner's shop; yet, unaccustomed to the rigors of working class manual labour, her rate of production is low and the quality of her workmanship is poor, and is fired at the end of the New York social season, when the demand for fashion hats has ceased.
Meanwhile, Simon Rosedale, a Jewish suitor who earlier had proposed marriage to Lily, when she was higher in the scale of social classes, returns to her life and tries to rescue her, but Lily is unwilling to meet his terms: Simon wants Lily to use love letters, which she bought from her servant, to confirm the occurrence, years earlier, of a love affair between Lawrence Selden and Bertha Dorset. For the sake of Selden's reputation, Lily does not act upon Rosedale's request, and secretly burns the love letters when she visits Selden, one last time.
In the event, Lily Bart receives a ten-thousand-dollar inheritance, from her Aunt Peniston, with which she repays Gus Trenor. Distraught by her misfortunate life, Lily had begun regularly using a sleeping draught of chloral hydrate to escape the pain of poverty and social ostracism; yet one day, Lily overdoses the sleeping draught, and kills herself. Hours later, Lawrence Selden arrives to her quarters, to finally propose marriage, but finds Lily Bart dead; only then was he capable of being close to her in the way he had proved incapable when she was alive.