Chad hosts a large, elaborate party to present to Sarah his whole society, hoping to impress upon her the fact that he is a "gentleman" in Paris in his own right. Chad has treated Sarah beautifully, but Strether doubts whether she is softening at all. He knows one thing — when her course is decided, he will "receive her entire weight." Seated on a divan at the party, Strether and Little Bilham candidly discuss Sarah's reaction to the affair. Bilham says Sarah is pleased with what Chad can do but is determined he shall do it in Woollett where she herself can be in command.
Strether begins to talk of Mamie Pocock and tells Bilham he wishes he would marry Mamie. He adds, "I want to have been at least to that extent constructive — even expiatory." Agreeing that a romantic attachment between Chad and Mamie is impossible, Bilham says, "She doesn't want to profit by another woman's work — she wants the miracle to have been her own miracle."
Strether talks to Miss Barrace next, and they speak of Waymarsh's abandonment of her for Sarah. Miss Barrace laughs and says, "Well, she thinks she has had her own way." She asks him not to let Chad go, and he answers that it is beautiful the way they all simplify when they want to. Strether winces at her prophetic response, "It's nothing to the way you will when you must."
Miss Barrace informs him that Madame de Vionnet is entertaining Jim Pocock at the party, and they agree that the idea is humorous and that Madame de Vionnet is indeed brave. Strether suddenly sees it in another light. "How indeed then she must care!"
In this chapter, Strether deepens his resolve to aid Chad and Madame de Vionnet; he also becomes more aware of how deeply Madame de Vionnet cares for Chad.
Notice that when Strether is told that he is looked upon as the "hero" who will save Chad, he takes the view that it is the "heroine" (by which he means Madame de Vionnet) who is in need of help.