Strether goes to Sarah's hotel, and though the servant admits him to her apartment, he sees no one in the room. His attention is directed to a table on which sits an unopened letter from Mrs. Newsome. "It had altogether such an effect upon him as made him for a few minutes stand still and breathe low." He realizes that even though Sarah is keeping him in the dark about her mother's thoughts, Mrs. Newsome is indeed corresponding with her daughter on a grand style.
His thoughts are interrupted when he notices a figure on the balcony. It is Mamie, and when she finally turns, she says, rather disappointedly, "Oh I thought you were Mr. Bilham!" During their conversation, Strether is certain that Mamie is actually on Chad's side, though they skirt actual mention of the situation. Mamie has visited the de Vionnets and "abounded in praise of them." When they discuss Jeanne's engagement, Mamie talks freely of her relief at discovering that Monsieur de Montbron is "perfectly gone" on Jeanne. She says that Jeanne doesn't know if she's in love or not, that she "doesn't know what's the matter with her[self]." That "was as near as they came to saying that she [Jeanne] was probably in love with Chad."
Mamie hopes to win Jeanne's confidence. She will tell her, she says good-humoredly, that she wants "too much to do right," to please. She wishes to please her mother, and then Chad, and, "last only," Monsieur de Montbron.
Frankly admiring her, Strether leaves her to await Bilham.
Mamie's touch of disappointment that it is Strether, not Bilbam, who has come into the room is a clue to the reader of what direction the narrative will take in regard to Bilham's role in the latter part of the novel. Notice also that Mamie is discovered by Strether as she is on the balcony, her arms on the railing, looking down into the street — almost precisely the manner in which Bilham is first seen by the reader.
The reference to Fromentin's "Maîtres d'Autrefois" is to Eugène Fromentin, a French painter whose studies of painters was published in 1876.