"I know how it will be," his sister had said when he was preparing to migrate to this rural retreat; "you will bury yourself down there and not speak to a living soul, and your nerves will be worse than ever from moping. I shall just give you letters of introduction to all the people I know there. Some of them, as far as I can remember, were quite nice."
Framton wondered whether Mrs. Sappleton, the lady to whom he was presenting one of the letters of introduction came into the nice division.
You must first understand that four years ealier Framton's sister had gone to visit people in that part of the country. She therefore knew a number of families in the neighborhood. She wrote letters of introduction to those she did know so Framton might visit them when he went there. One may not visit socially without a proper form of introduction from a mutual acquaintance.
Secondly, you must understand that for some reason we are never told Framton has a nervous disorder that is significant enough to be sent to the country to rest and recuperate. Thus, Framton is going to rest in the country in the same neighborhood his sister stayed in.
Finally you must understand that Framton's sister, whose name we are never given, believes that if Framton doesn't get out and visit people he will dwell unhappily all alone all the time and, in so doing, will worsen rather than better his nervous disorder. Now we can say that the reason Framton Nuttel visits Mrs. Sappleton is that his sister told him to and gave him a letter of introduction because she and his sister had been acquainted, and Framton was in the country to recover from his nervous illness--but--is not permitted to stay alone all the time.