“Watching is like nature photography: You don’t interfere with the wildlife.” 

Anna watches her neighbors through her windows, and when she wants to see something or someone more clearly, she uses the high-powered zoom lens on her camera to focus on her subject. In this quote, Anna compares her neighbors to animals in nature; this comparison heightens the reader’s appreciation of Anna’s sense of isolation. Nature photographers need to obscure themselves to avoid startling the animals they hope to capture on film, just as Anna hides behind her curtains and walls to avoid discovery by her neighbors.

“I don’t know. The first profile I spotted was David’s. I instantly deleted my account.” 

Anna’s brief mention of a dating app foreshadows her sexual encounter with David, her tenant, later in the novel. David’s appetite for physical entanglements with women are well-documented by Anna, and his attractiveness to women also appears remarkable; in a different situation, Anna may have become involved with David after meeting him on Tinder.

“He’s tall indeed, baby-faced and blue-eyed, with a flap of sandy hair and a faint scar notching one eyebrow, trailing up his forehead. Maybe fifteen years old. He looks like a boy I once knew, once kissed—summer camp in Maine, a quarter century ago. I like him.” 

In this passage, Anna describes Ethan to the reader, and this introduction to Ethan is disarming. The fact that Anna, the narrator of the novel, likes Ethan and compares him to a memory of a boy she once liked gives reader a false sense of security, which heightens the drama of the big reveal at the end of book: Ethan is guilty of murder.