Bethlehem Road - Anne Perry

He might be elegant, but there's no mistaking it--the gentleman tied to the lamppost on Westminster Bridge is definitely dead. Before Inspector Thomas Pitt can even speculate on why anyone should want to kill the eminent M.P., Sir Lockwood, a colleague of his, meets the same fate at the same spot. The public is outraged, and clever Charlotte Pitt, Thomas's well-born wife, helps her hard-pressed husband by scouting society's drawing rooms for clues to these appalling crimes. Meanwhile, another victim is being stalked....
"Mrs. Perry once again demonstrates her true and lively passion....Her finely drawn characters couldn't be more comfortable within the customs and sensibility of their historical period."
THE NEW YORK TIMES BOOK REVIEW