Social Crimes by Jane Stanton Hitchcock. From Amazon: "When Jo Slater, one of New York’s premier socialites and a patron of the arts, befriends a French countess, she ignores warnings from friends about the mysterious newcomer. Soon, the young woman knocks Jo off her Park Avenue throne. But using her knowledge of the greatest historical swindle of all time—a true story involving Marie Antoinette—Jo sets out to reclaim her fortune and her place in society. For the plan to work, however, she must resort to the most desperate of measures: murder. Social Crimes is a savvy social satire bursting with money, betrayal, and passion that will thrill readers of sophisticated mysteries."
