Mr and Mrs Emerson Sillerton invite the Wellands to a party for the Blenkers. Mr Welland makes his excuses, but Mrs Welland decides that she will call in briefly, so that the Sillertons are not offended. Archer says he will drive to a stud farm to look for a second horse for May's carriage.
Though Archer does call at the stud farm, he really wants to see the Blenkers' house because Ellen is living there. If he could carry away that vision, the rest of his world would seem less empty. He thinks that Ellen will be away from home, in Newport with the Blenkers, or visiting her grandmother, Mrs Mingott.
He sees a pink parasol in the summer-house, and, believing it is Ellen's, heads towards it. But it belongs to one of the Blenker girls. Miss Blenker says that Ellen has been called away to Boston.
Archer tells May that he has to go to Boston on business. He even uses a letter that arrives for him from the office to justify his plan - a deception which reminds him of the adulterer Lefferts's contrivances. In Boston the next day, he sees Ellen sitting on a bench on the common. She says she is here on business. She tells him that she has refused to take back money that belonged to her, because she could not agree to the conditions - to sit at the head of her husband's table occasionally. Count Olenski had not come himself, but had sent an emissary. Archer thinks this is the man with whom Ellen reportedly had the affair. The emissary is waiting till tonight before leaving, in case she changes her mind.
Archer asks her to spend the day with him. She asks him why he did not come down to the beach to her when she was at Mrs Mingott's. He says, because she didn't look round at him. She says she did not look round on purpose and that she was trying to get as far away from Archer as she could. He tells her that he has come to Boston to see her. She goes back to her hotel to leave a note for the emissary, where Archer sees a man whose face he half-recognizes.
Ellen joins Archer and tells him of her life in the one and a half years since they met. She had grown tired of New York society, feeling herself too different to care for the things it cared about. So she had settled in Washington, where there were supposed to be more varieties of people and opinions.
Archer wonders why she does not go back to Europe. She says, because of him. She starts to tell Archer how he has changed her, but he interrupts her by saying how she has changed him: "I'm the man who married one woman because another one told him to." She says that he has given up something he wanted (her) to save others (May) from disillusionment and misery; at least May is happy. If this was not a worthwhile sacrifice, then everything she has come to value in her "new" life is a sham.
Archer savagely says that she gave him his first sight of real life, and at the same moment asked him to go on with a sham one. She bursts into tears, confessing that she is suffering just as he is. Archer feels overwhelmed by a sense of waste, chained as they are to their separate destinies. She promises him that she will not go back to Europe as long as they do not act on their love for each other.
Ellen's comment to Archer that she finds Dr Carver's crazy social schemes more interesting than the blind conformity to tradition that she finds in New York society is revealing. As she points out, that tradition is not even America's own - it is borrowed from the old European countries from which the settlers came: "It seems stupid to have discovered America only to make it into a copy of another country."
The tragic element of the novel reaches its apotheosis in the scene between Archer and Ellen in Boston. He realizes that if he acts on his love for her, he will drive her away, so much has she taken to heart his previous arguments that it is wrong to buy one's happiness at another's expense. She will stay only if he and she are not together. The individual has been sacrificed at the altar of the family and society.
However, Wharton undermines Archer's tragic status by comparing his easy deception of May in visiting Boston to the contrivances of the adulterer Lefferts. Are they different? If we saw events from Lefferts's point of view instead of Archer's, would we sympathize with him as much? Wharton creates some sympathy for Archer by distinguishing his feelings for Ellen from his more superficial feelings for May. While he had been awed by May's physical beauty, he feels a "curious indifference to [Ellen's] bodily presence"; his connection with Ellen is more intellectual and emotional.
We learn that Ellen knew Archer was at the beach when he was asked to fetch her by Mrs Mingott. Archer had put their failure to speak to each other down to the fate that caused her not to turn round and see him. But in fact, both consciously chose not to speak; the responsibility for their not meeting lies with them, and not chance or fate.