The Age of Innocence centers on an upper-class couple's impending marriage, and the introduction of the bride's cousin, plagued by scandal, whose presence threatens their happiness. Though the novel questions the assumptions and morals of 1870s New York society, it never develops into an outright condemnation of the institution.The novel is noted for Wharton's attention to detail and its accurate portrayal of how the 19th-century East Coast American upper class lived, and the social tragedy of its plot. Wharton was 58 years old at publication; she had lived in that world and had seen it change dramatically by the end of World War I.
The title is an ironic comment on the polished outward manners of New York society when compared to its inward machinations. It is believed to have been drawn from the popular 1785 painting A Little Girl by Sir Joshua Reynolds that later became known as The Age of Innocence and was widely reproduced as the commercial face of childhood in the later half of the 18th century. The title, while ironic, was not as caustic as the title of story featured in the The House of Mirth, published in 1905.Newland Archer, gentleman lawyer and heir to one of New York City's best families, is happily anticipating a highly desirable marriage to the sheltered and beautiful May Welland. Yet he finds reason to doubt his choice of bride after the appearance of Countess Ellen Olenska, May's exotic and beautiful 30-year-old cousin. Ellen has returned to New York from Europe after scandalously separating herself (per rumor) from a bad marriage to a Polish count. At first, Ellen's arrival and its potential taint on the reputation of his bride-to-be's family disturb Newland, but he becomes intrigued by the worldly Ellen, who flouts New York society's fastidious rules. As Newland's admiration for the countess grows, so does his doubt about marrying May, a perfect product of Old New York society; his match with May no longer seems the ideal fate he had imagined.
Ellen's decision to divorce Count Olenski causes a social crisis for the other members of her family, who are terrified of scandal and disgrace. Living apart can be tolerated, but divorce is unacceptable. To save the Welland family's reputation, a law partner of Newland asks him to dissuade Countess Olenska from divorcing the count. He succeeds, but in the process comes to care for her; afraid of falling in love with Ellen, Newland begs May to accelerate their wedding date, but she refuses.
Newland tells Ellen he loves her; Ellen corresponds, but is horrified that their love will aggrieve May. She agrees to remain in America, separated but still married to Count Olenski, only if they do not sexually consummate their love. Newland receives May's telegram agreeing to wed sooner.
Newland and May marry. He tries unsuccessfully to forget Ellen. His society marriage is loveless, and the social life he once found absorbing has become empty and joyless. Though Ellen lives in Washington and has remained distant, he is unable to cease loving her. Their paths cross while he and May are in Newport, Rhode Island. Newland discovers that Count Olenski wishes Ellen to return to him, but she has refused, although her family wants her to reconcile with her husband and return to Europe. Frustrated by her independence, the family has cut off her money, as the count had already done.
Newland desperately seeks a way to leave May and be with Ellen, obsessed with how to finally possess her. Despairing of ever making Ellen his wife, he urges her to become his mistress. Then Ellen is recalled to New York City to care for her sick grandmother, who accepts her decision to remain separated and agrees to reinstate her allowance.
Back in New York and under renewed pressure from Newland, Ellen relents and agrees to consummate their relationship. However, Newland then discovers that Ellen has decided to return to Europe. Newland makes up his mind to abandon May and follow Ellen to Europe when May announces that she and Newland are throwing a farewell party for Ellen. That night, after the party, Newland resolves to tell May he is leaving her for Ellen. She interrupts him to tell him that she learned that morning that she is pregnant; she reveals that she had told Ellen of her pregnancy two weeks earlier, despite not being sure of it at the time. The implication is that she did so because she suspected the affair. Newland guesses that this is Ellen's reason for returning to Europe. Hopelessly trapped, Newland decides not to follow Ellen, surrendering his love for the sake of his children, remaining in a loveless marriage to May.
Twenty-six years later, after May's death, Newland and his son are in Paris. The son, learning that his mother's cousin lives there, has arranged to visit Ellen in her Paris apartment. Newland is stunned at the prospect of seeing Ellen again. On arriving outside the apartment building, Newland sends up his son alone to meet Ellen, while he waits outside, watching the balcony of her apartment. Newland considers going up, but in the end decides not to; he walks back to his hotel without seeing her.
Output: Before Newland can tell may that  he is leaving her, what does she tell him?