Lily Bart is a beautiful but impoverished socialite, who is seeking a husband to secure her future. Her success is challenged by her advancing age — at twenty-nine, she has been on the "marriage market" for more than ten years — and her debts from gambling at bridge. While Lily admires the handsome and ambitious lawyer Lawrence Selden, he is too poor for her to seriously consider marrying; instead, her only prospects are the coarse and vulgar Simon Rosedale, a financier, and the wealthy but dull Percy Gryce.
Lily grew up surrounded by elegance and luxury — an atmosphere she believes she cannot live without. The loss of her father's wealth, coupled with the sudden death of her parents, left her an orphan at twenty. Lacking an inheritance or a caring protector, she adapts to life as a ward of her strait-laced aunt, Julia Peniston, from whom she receives an erratic allowance, a fashionable address, and good food, but little direction or parenting. Lily loathes the neglectful Julia and avoids her whenever possible but is forced to rely on her for her necessities and luxuries.
Lily learns that Selden and the vindictive heiress Bertha Dorset were once lovers. She also confides her money problems to Gus Trenor, a stockbroker and the husband of her childhood friend Judy, receiving from him a check for $5,000 and an investment of $4,000 in her name. Trenor tries to exploit his generosity to make a romantic move, but Lily spurns his attentions. Bertha still has feelings for Lawrence notwithstanding her recent breakup with him. When it becomes clear that Seldon still has feelings for Lily, she aims to ruin the latter's budding romance with Percy by filling him in on the most salacious and scandalous rumors about Lily's card-playing and past romantic life. This effectively frightens Percy away. Lily, unaware of Bertha's machinations, blames Judy for having been the one to set the match up.
In retribution for a social snub, Lily's cousin Grace Stepney informs Julia of rumors that Lily is having an affair with Gus to obtain money so she can pay off her gambling debts. This plants seeds of doubt and discomfort in Julia who, though shocked, chooses to accept the rumors without speaking to her niece.
The tragic heroine of The House of Mirth (1905), Lily Bart, lingers at the broad staircase, observing the high-society people gathered in the hall below.Furthermore, Lily has soured her relationships with both Gus, who is angered by her spurning him, and Judy, because she refuses to visit her at Bellomont lest Gus confront her and reveal that she had manipulated him for financial gain.
To avoid having to spend time alone with her aunt, the Trenors, Simon Rosedale, or anyone else she considers a possible source of embarrassment or boredom, Lily begins to accept invitations from people with whom she would not ordinarily socialize. These include the Wellington Brys, who are newcomers to the New York social scene, and whose social rise is being engineered by Carry Fisher. Carry, a fallen aristocrat who supports herself by acting as a social secretary to usher newly wealthy people into fashionable society, invites Lily to social events hosted by Louisa Bry. Lily also attends the opera with Carry, Simon, and Gus. In the eyes of high society, Lily cheapens herself by voluntarily associating with her social inferiors. She returns briefly to Bellomont only to find that her peers now look at her with derision and disgust.
One of Julia's temporary servants, who is also the charwoman at Selden's apartment, sells Lily a package of torn love letters. These were written by Bertha Dorset years earlier, and they represent a chance for Lily to deal with her enemy. But instead of blackmailing Bertha into a positive relationship, Lily tries to neutralize the gossip by making herself useful to Bertha. Bertha, who is sleeping with Ned Silverton, relies on Lily to distract her husband, George.
The extent to which Lily's reputation is damaged becomes obvious when she publicly appears in a way that comes across as advertising her availability for an illicit relationship. Following Carry's advice, the Wellington Brys throw a large "general entertainment"[12] featuring a series of tableaux vivants portrayed by a dozen fashionable women in their set, including Miss Bart.
The pièce de résistance of this highly successful event turns out to be the portrayal of Mrs. Lloyd in Sir Joshua Reynolds' famous 18th-century painting (1775–1776). The portrait shows an attractive woman suggestively clad.[h][14] As the curtain opens on this last scene, the gasp of approval heard from the audience was not so much for Reynolds’ brilliant interpretation of Mrs. Lloyd as it was for the loveliness of Lily Bart herself — marking the pinnacle of her social success but also the annihilation of whatever reputation is left to her. For better or for worse, she has transitioned from a marriageable "girl" to a not-quite-reputable woman similar to Carry Fisher. Yet she does not do as Carry Fisher does and accept the loss of her respectability as the price, she must pay to maintain a position in society.
As Selden observes her in this elegantly simple tableau, he sees the real Lily Bart as if for the first time[i] and feels the desire to be with her. He finds her alone in the ballroom toward the end of the musical interlude, as the collective praise from her admirers is subsiding. He leads her to a garden where he tells her he loves her and they kiss. Lily sighs, " 'Ah, love me, love me—but don't tell me so!' " and takes her leave.[j] As Selden gathers his coat to leave, he is disturbed by Ned Van Alstyne's remarks, ". . . .Gad, what a show of good-looking women; but not one of 'em could touch that little cousin of mine. . . . I never knew till tonight what an outline Lily has."
Lily pleads with her aunt to help settle her debts and confesses her addiction to gambling. Julia feels taken advantage of and refuses to help her, except to cover the bill for her clothes and accessories. Feeling trapped and disgraced, she turns to thoughts of Selden as her savior and has a change of heart towards him as she looks forward to his next visit at four o'clock.
Instead, her visitor turns out to be Simon Rosedale who, so smitten by her appearance in the tableau vivant, proposes a marriage that would be mutually beneficial. Considering what Rosedale knows about her, she skillfully pleads for time to consider his offer [k] Selden does not appear for his 4:00 appointment nor does he send word in explanation. Instead, she learns that he has departed for Havana and then on to Europe for a business trip.
To escape the rumors arising from the gossip caused by her financial dealings with Gus, and also disappointed by what she interprets as Selden's emotional withdrawal, Lily accepts Bertha's spur-of-the-moment invitation to join her and George on a Mediterranean cruise aboard their yacht; Lily is expected once again to hide Bertha's affair. Lily's decision to accept the offer proves to be her social undoing.
In order to divert the attention and suspicion of their social circle away from her, Bertha insinuates that Lily is carrying on a romantic and sexual liaison with George by instructing her not to sleep on the yacht in front of their friends at the close of a dinner the Brys held for the Duchess in Monte Carlo. Selden inadvertently helps by arranging a night's lodging, under the promise that she leave promptly in the morning. The ensuing social scandal ruins Lily's reputation and almost immediately causes her friends to abandon her and Julia to disinherit her.
Undeterred by such misfortunes, Lily fights to regain her place in high society by advising Mr. and Mrs. Gormer on their entry into the aristocracy, but when the couple learn from Bertha the "scandalous" personal background of their new secretary, they are quick to chase her out rather than risk losing their new standing. Only two friends remain for Lily: Gerty Farish (a cousin of Lawrence Selden) and Carry, who help her cope with the social ignominy of a degraded social status while continually advising Lily to marry as soon as reasonably possible.
Despite the efforts of both Carry and Farish, Lily rapidly descends through the social strata of New York City's high society. She obtains a job as personal secretary of Mrs. Hatch, a disreputable woman who very nearly succeeds in marrying a wealthy young man in Lily's former social circle. It is during this occupation she is introduced to the use of chloral hydrate, sold in drugstores, as a remedy for malaise. She resigns her position after Hatch blames her for the failure of her engagement. Lily then finds a job in a milliner's shop; unaccustomed to the rigors of working-class manual labor, her rate of production is low, and the quality of her workmanship is poor, exacerbated by her increased use of the drug. She is fired at the end of the New York social season, when the demand for fashionable hats has diminished.
Meanwhile, Simon reappears in her life and tries to rescue her, but Lily is unwilling to meet his terms. Simon wants Lily to use the love letters that she bought from Selden's servant to expose the love affair between Lawrence and Bertha, thus crushing a potential rival and allowing him to further ascend up the social ladder. For the sake of Selden's reputation, Lily does not act upon Rosedale's request and secretly burns the letters when she visits Selden one last time.
Lily is stopped on the street by Nettie Struther, who Lily once helped get to a hospital. Nettie is now married and has a baby girl, and she invites Lily to her apartment to work as a nursemaid for her daughter.
Eventually, Lily receives a ten-thousand-dollar inheritance following Julia's death, which she uses to repay Gus. Distraught by her misfortunes, Lily is now crippled by drug dependence. Once she has repaid all her debts, Lily takes an overdose and dies; perhaps it is suicide, perhaps an accident. As she is dying, she hallucinates cradling Nettie's baby in her arms. That very morning, Lawrence arrives at her quarters, to finally propose marriage, but finds Lily dead. Among her belongings are bank receipts proving her dealings with Gus were honorable and that the rumors that destroyed her were false from the beginning. This realization allows him to feel sympathy for her, and he is clearly distraught at her death.
