Death, Diamonds, and Deception is the fifth book in Rosemary Simpson’s Gilded Age mystery series set in New York City in the 1880s. It’s the first I’ve read, but I enjoyed it so much that I will definitely look for the others. The two protagonists are heiress Prudence MacKenzie and ex-Pinkerton agent Geoffrey Hunter, who are partners in a detective agency. Prudence is the daughter of a wealthy judge, a prominent man in New York, who died about two years before this book begins. She is part of the city’s elite, the world of the Astors and Vanderbilts, even though she defies the standards of that society by becoming a detective. Geoffrey is a Southerner who came to New York around the time of the Civil War because he was anti-slavery. He is quite a bit older than she is. Prudence is around twenty, and, although Geoffrey’s age is not specified, it seems that he was already an adult at the time of the Civil War, so he must be in his early forties at least.