On a beautiful sunny day, a young woman named Cora Tannetti, in a fit of unexplained rage, stabs a stranger to death with a fruit knife. The crime is witnessed by an uncomprehending husband, a terrified son, and dozens of shocked vacationers. Everyone knows who did it, but no one understands the reason, including Cora herself. Detective Harry Ambrose sets out to uncover the motives behind Cora's use of the fruit knife. He is willing to spend as much time as necessary with the criminal, delving into the depths of her psyche and uncovering her secrets to understand why a seemingly kind and law-abiding woman would commit such a heinous...