The passage reflects on the tension between the arrival of Harriet, Ron's intended, and the impending departure of Brenda. The narrator suggests that Harriet’s arrival casts a shadow, symbolizing the passage of time and changes in relationships. It implies that such transitions can evoke a sense of darkness, perhaps due to the emotions tied to these changes.

This moment also highlights the inevitability of life’s transitions, as the characters grapple with the fleeting nature of time. The comparison between Harriet's arrival and Brenda's departure emphasizes a growing awareness of life's cyclical nature, encapsulating a blend of anticipation and melancholy.