A smooth seducer who kills women he meets on luxury cruises would seem to be a natural for Clark (Pretend You Don't See Her, 1997, etc.). But the devil isn't in the details this time, and a series of miscues lets the tension escape from her 16th novel. Why do women vanish? clinical psychologist Dr. Susan Chandler, host of radio's Ask Dr. Susan, asks her guest Dr. Donald Richards, author of Vanishing Women. The main answer, of course, is that they're preyed upon by unscrupulous men. One such victim was Regina Clausen, who never returned to her ship from an excursion to Hong Kong three years ago. Now Carolyn Wells, a caller to Susan's show, reveals that she may have been the intended prey of a similar villain--a man who left her holding a photograph and a turquoise ring inscribed ""You belong to me"" when she escaped back to the arms of her jealous husband Justin. Susan and Don are both excited about the possible link to Regina Clausen's disappearance. But before Susan can meet Carolyn and examine the ring and photo, Carolyn's pushed under the wheels of a van by a man who walks off with the evidence. It's only the first of a series of four murderous assaults by an unusually enterprising killer bent on covering his tracks--a killer who's hiding in a thicket of handsome gentlemen with a special affinity for good-looking women and luxury cruises. So far so good; but this time the killer, for all his industry, is toothless--partly because his target victim isn't Susan but her forgettable sister Dee, who prattles about going on a cruise till you wish she'd just go ahead and get herself killed, partly because Susan, more detective than victim, is clearly more than a match for the predator. All the usual trappings of upscale menace except the menace. Wait till next year's cruise.