"The Husband's Secret" is a novel by Liane Moriarty that explores the lives of three women whose paths intertwine in unexpected ways. The story centers around Cecilia Fitzpatrick, who discovers a letter written by her husband, John-Paul, meant to be opened only in the event of his death. The contents of the letter reveal a shocking secret that challenges Cecilia's perception of her marriage and her life. As the narrative unfolds, readers also meet Tess and Rachel, two other women grappling with their own personal struggles. The novel delves into themes of love, betrayal, and the complexities of relationships, ultimately leading to a dramatic climax that forces each character to confront their choices and the consequences of their actions.