Though the two women live just a few doors apart, a chasm lies between them. The actress, a celebrity with a charmed career, shares a gleaming brownstone with her handsome husband and three adorable children, while the recently separated narrator, unhappily childless and stuck in a dead-end job, lives in a run-down, three-story walk-up with her ex-husband’s cat. As her fascination with her famous neighbor grows, the narrator’s hold on reality begins to slip. Before long, she’s collecting cast-off items from the actress’s stoop and fantasizing about sleeping with the actress’s husband. After a disastrous interaction with the actress at the annual block party, what began as an innocent preoccupation turns into a stunning—and irrevocable—unraveling.