The latest in the Ben Franklin series (Murder at Drury Lane, 1992, etc.) finds the renowned statesman, inventor, and sleuth searching for the lost Shenstone diamond. The gem, which disappeared while being painted onto a portrait of Lady Shenstone, is worth a king's ransom, and the lady is desperate to retrieve it before her husband learns of its absence. To this end, she engages Mr. Franklin, who takes on such cases to relieve the boredom of political life in London. Franklin places his illegitimate son, Nick Handy, in the studio of James Cavitty, the painter, to discover what he can. What Nick discovers is that the artist's household is rife with intrigue -- secret lovers, mysterious engravings -- and that any number of people, both in and out of the house, might have taken the precious stone. When Nick finds Cavitty dead among his paintings, Franklin takes over the murder investigation as well. Was Cavitty killed for the Shenstone diamond, or could it have something to do with a destroyed copperplate? Leave it to the man who discovered electricity to find out. A charming little mystery, cleverly plotted with nice 18th-century flavor.