The Age of Innocence Chapter 3
After the opera, the audience goes to the home of Julius Beaufort and his wife, Regina Beaufort, for their annual ball. Although New York society distrusts Julius Beaufort because he has "common" roots, they all agree that the Beauforts have the best ballroom in the city. Archer, as usual, arrives fashionably late. He is nervous that May's family might bring Ellen to the ball. Judging from the men's gossip at the opera, Archer knows that Ellen's appearance at this ball would be a social blunder.
When he enters the ballroom, he sees May announcing their engagement to a group of young people. Archer and May both know that a ballroom is not an ideal place to make such an important announcement, but it's necessary. They both want to take some attention off of Ellen and show the family in a positive light.
Archer goes up to the crowd and draws May onto the dance floor. After the dance ends, they walk to the conservatory to talk privately. May asks if he had told Ellen of the engagement, and is disappointed when she learns that he had not. She asks him again to tell her cousin, and Archer agrees.
He is relieved when May tells him that Ellen decided not to come to the ball because her dress wasn't fancy enough. However, both Archer and May know the real reason why she decided to go home. Archer admires May's commitment to ignoring the unpleasant circumstances that surround Ellen. He makes a decision: "I shall never let her see by the least sign that I am conscious of there being a shadow of a shade on poor Ellen Olenska's reputation." Chapter 3, pg. 27