The sixth outing for Denver insurance investigator Hobart Lindsey (The Cover Girl Killer, 1995, etc.) once again colors a modern mystery with historical sidelights. This time Lindsey is in Manhattan, where colleague Cletus Berry has been found shot in an alley, along with a small-time gangster. The chief clue? An insurance policy in Berry's computer, dating from the New York World's Fair circa 1940--when a priceless exhibit, a toy chariot once owned by Julius Caesar, disappeared on its way home to Rome. Maybe it's no coincidence, then, that Berry was with the US Army in Italy in the 1970s (where he met his Jewish-Italian wife). Or that the other alley victim had links to a shady Manhattan antique dealer. Or that a rising New York demagogue is using the Caesar chariot as his logo. So, as more bodies drop, the action shifts to Italy for a treasure-hunt finale--with Lindsey side-kicked by Berry's brother, a retired cop. (His usual sleuth-mate, Marvia Plum, is out of the picture, having married someone else.) Lupoff's latest concoction strains a bit under the weight of cutesy Maltese Falcon references, classical allusions, movie-trivia repartee, Holocaust-tinged secrets, and more. But, with quietly engaging Lindsey at the center, this leisurely, fanciful whirl of subplots and curious digressions holds some old-fashioned appeal, if few surprises.