It is 1995, and American author Highsmith (Mirren), now in her seventies and in poor health, has retired to the Swiss Alps, where she largely confines herself to her study, surrounded by her books, her cats, and her collection of antique weapons. Enter Edward Ridgeway (Ehrenreich), emissary for a New York publisher sent to persuade Highsmith to craft one last instalment in her bestselling series of mysteries featuring the murderous antihero, Tom Ripley. Irritated by this youthful, overly eager visitor, Highsmith refuses the offer — unless, that is, Ridgeway can dream up the perfect murder along with her.