When describing the solitary way in which Phyllis and her father (Dr. Grove) live, the narrator uses a pair of metaphors, as seen in the following passage:
The daughter’s seclusion was great, but beyond the seclusion of the girl lay the seclusion of the father. If her social condition was twilight, his was darkness. Yet he enjoyed his darkness, while her twilight oppressed her.
The narrator metaphorically compares Phyllis’s “social condition” to “twilight” and her father’s to “darkness.” These metaphors help readers understand that, though Phyllis does not have much “light” (or socializing) in her life, she at least has some, as twilight is the time of day between light and dark. Dr. Grove, on the other hand, seemingly does not socialize with anyone, and therefore lives in “darkness” (which he “enjoy[s]”).
That Phyllis experiences her lack of social life as “oppressive” helps readers understand why Matthäus’s presence ends up becoming so comforting and life-giving for her. Though she is technically engaged to Humphrey, he proposed to her out of the blue and then left their village for a full year. Because Dr. Grove does not enjoy company and keeps Phyllis from going off on her own, Phyllis’s only hope for human contact is via Matthäus’s visits to her garden.