Wallace's novels may not be getting any better--if anything, they've become even more clunky, with the most mechanical, unerotic sex scenes on record--but he still has an undeniable knack for hammering away at a single familiar theme through a crudely linear plot. Here it's mankind's lust for the Fountain of Youth, which Prof. Davis MacDonald seems to have found and somehow distilled in the Soviet Caucasus. (He must have seen those yogurt commercials.) Even vaguely knowledgeable readers will raise eyebrows at Wallace's comic-book science here, but Russian authorities go wild--they want the formula for Russia alone! So MacDonald escapes onto a Venice-bound plane in order to bring his discovery to the whole world. Venice, however, has a Communist mayor, who allows the Prof to be abducted to a monastery on the canal island of San Lazzaro. Will he escape? Of course he will--thanks to American PR man Tim Jordan, who picks up a wounded pigeon in Piazza San Marco and finds the Prof's cry-for-help tied to the pigeon's leg. He contacts the Prof's comely colleague, and together they spring the Prof and then try a half dozen different hideouts, disguises, and escape plans for the Most-Wanted fugitive. (Venice has declared a state of emergency to contain and capture this supposed escaped ""spy."") But in each and every case, success is dashed because whenever a presumed ally--even the Pope!--learns of the Prof's secret long-life serum, he or she goes bananas with selfish ruthlessness. And so it goes--till the Prof is dead and so is the formula, purposely destroyed by our sadder-but-wiser hero. Shamelessly padded with chunks from Venice tourguides and debates on the pros and cons of a 150-year life span, this is the nth degree in bumpy predictability--but there's a certain intermittent energy in Wallace's noisy simplemindedness.