A woman's body surfaces in a lake, and Detective Superintendent Peter Diamond must find two lost Jane Austen letters to solve the murder and clear an innocent woman. The victim, identified only as the 'Lady in the Lake,' bears no visible wounds, and no murder weapon is found, presenting Diamond with a perplexing case. As one of the last detectives to rely on traditional methods of questioning and deduction, Diamond finds himself at odds with his superiors. His investigation into the murder leads him to search for two missing letters attributed to Jane Austen, a pursuit that becomes crucial to uncovering the truth and saving a woman wrongly accused.

The introduction by Louise Penny highlights this series as trend-setting and beautifully written, setting a high expectation for the novel. The book's win of the 1992 Anthony Boucher Award for Best Mystery Novel indicates critical acclaim within the genre. The premise suggests a classic detective story focused on meticulous investigation and character-driven deduction. The inclusion of historical elements, specifically Jane Austen's letters, adds a unique layer to the mystery, promising an engaging narrative for fans of historical mysteries and traditional detective fiction.