When six months have elapsed, Newman again raises the question of marriage to Claire, and this time she accepts his proposal, although still with doubts and worries. While Newman is elated about his engagement, the Bellegarde family reacts coldly to the news, with the exception of Valentin. Mrs. Bread expresses cautious happiness but advises him to marry as quickly as possible, lest something go wrong.
In his excitement, Newman wants to throw a party, hoping to bring together French and American friends. Madame Bellegarde seems to dislike this proposal, and insists on throwing her own part first to introduce Newman to the connections of the family.
Meanwhile, Newman hears that Noemie has left her father's house and been installed as the mistress of a wealthy man. Monsieur Nioche stops visiting Newman, and Newman, worried, tracks him down at his local café, where he is surprised to find both father and daughter together. Noemie is unashamed that she is advancing her position through her sexuality. While her father claims to object to her behavior, he also willingly takes money from her. Despite this, Valentin also continues to visit her, and finds himself melancholy due to his attraction to her.
The ball thrown by Madame Bellegarde is a very grand occasion and offers a spectacle of wealth among the Parisian elite. Newman feels slightly self-conscious about being the center of attention, but is filled with triumph that he has won Claire as his wife.
Over the course of the evening, he comes across first old Madame Bellegarde, and then Claire, involved in intense conversations with Lord Deepmere. He is curious about the nature of these conversations, but Claire declines to explain, and he is too focused on enjoying his night to probe the matter further.
Shortly after the party, Newman is attending the opera on a night that Urbain, his wife, Valentin, and Noemie are all also present. Noemie is being courted by a young German man named Stanislas Knapp. Valentin complains about Noemie to Newman, but clearly still harbors feelings for her. Young Madame Bellegarde, Urbain's wife, also takes the opportunity to tell him how trapped and restricted she feels in her life.
During the course of the opera, Stanislas and Valentin get into a quarrel and agree to a duel to settle their honor. Noemie is delighted, since this will help her to further her reputation for desirability. Newman is nervous about this, but Valentin seems calm and leaves for Switzerland, where the duel is to take place, the next day.
The intersection of sex, money, and complicated motives dominate this section. Newman seems blissfully naïve throughout, focusing single-mindedly on the fact that he has persuaded Claire to marry him. Her acceptance of his proposal is lackluster and ambivalent, but he ignores this in his focus on his triumph. He also overlooks other warning signs such as the displeasure from her family, the apparent concealment of some plan or scheme with Lord Deepmere, and Mrs. Bread's worries and doubts. All of these signs foreshadow that despite their engagement, problems still lie ahead for Claire and Newman.
While Claire remains obscure, two other female characters reveal a complexity of motives and desires. Noemie has broken with social convention and distressed her father by moving out and continuing relationships with men who support her financially. She however sees this behavior as one of the few options available to her to make a better life, and doesn't hesitate to use it. Young Madame Bellegarde also reveals her resentment; even though she has wealth and a title, she longs for more experiences and the freedom to experiment and make her own choices. In the desires they express, both women challenge Newman's idealized view of women as delicate, helpless, and in need of protection, but he fails to connect their behavior to Claire. He also breaches expectations of honorable and gentlemanly behavior when he bluntly refers to Noemie as a whore when trying to dissuade Valentin from dueling on her behalf.
Newman's willfully ignorant behavior is on display both at the party, and when he fails to take account of the reaction of the Bellegarde family to his engagement. Despite their ostensible willingness to support him, they are clearly not pleased with the reality that he is now going to marry Claire. It may be that they believed Claire would never actually agree to an engagement, or that they have now had an offer that would combine both wealth and status. The interactions between Claire, Madame Bellegarde, and Lord Deepmere are suspicious, and yet Newman is too caught up in self-confidence and his sense of triumph to be worried. As he believes that he is such a desirable husband, he has a hard time understanding that anyone else might think otherwise.
While Valentin is in many ways a foil to Newman, he is also capable of acting irrationally. While he repeatedly understates his feelings for Noemie, he is unable to completely cut ties with her. The tensions created when desire cuts across class lines and social hierarchies is further demonstrated in this subplot: Newman's desire for a woman who is socially superior risks making him unhappy, while Valentin struggles with the challenges of being attracted to a woman who is decidedly his social inferior, a fact he acknowledges when he repeats several times that he would never consider marrying Noemie.
Dueling (a pre-arranged confrontation between two individuals with weapons agreed upon ahead of time, and carefully orchestrated rules) had a long history, especially among members of the social elite. Fighting duels was linked to an insult to one's honor; certain situations were perceived as able to be resolved only by the display of courage involved in risking one's life, thus displaying one's valor and manliness. Duels played an active role in American social codes as well (Alexander Hamilton, for example, was killed in a duel with a political opponent in 1804). However, dueling as a practice declined more quickly in America and Great Britain than it did in other parts of Europe, and this contrast can be seen in James's novel. To Newman, the practice is old-fashioned and barbaric; he considers his integrity to be tied to honesty and success, not an abstract sense of honor. For Valentin however, defending his honor is as necessary as respecting the traditions of his family and behaving according to socially accepted norms.