A Lesson in Secrets is a compelling mystery novel by Jacqueline Winspear that delves into the life of Maisie Dobbs, a former nurse and now a private investigator. Set in the early 1930s, the story unfolds as Maisie is tasked with an undercover mission at a progressive school in Cambridge. The institution, which aims to foster new ideas about education, becomes the backdrop for a series of intriguing events that touch upon themes of loyalty, trust, and the impact of war on society.