If you are a fan of Jacqueline Winspear’s mysteries set in London between the World Wars, when you read her last book (A Lesson in Secrets) you might have thought Maisie Dobb’s life was getting comfortably settled. Without any soap opera antics, just Winspear’s impeccable, nuanced character development, Maisie is at sea again in a variety of ways, and she’s solving a mystery of a completely new sort. Eddie is a “slow” man who has a magic way with horses. When he dies in an “accident,” the cockney costermongers of Maisie’s childhood feel justice hasn’t been done and they come to see her. You wouldn’t think this would involve issues of national safety, now would you?