Imagine Hannibal Lecter with a social conscience, and you'll have the germ of Hall's diabolically sharp new thriller. Bill Kaiser is a man with a mission: He wants a Manhattan day-care center installed in the decaying Carnegie-Hayden building so much that he's willing to kill the project's opponents. Captured by the police after planting a bomb in sanctimonious Senator Arvin Redwell's high-rise, Bill fakes insanity convincingly enough to get committed for three days' observation in Bellevue, where he puts on such a winning (though demented) front that psychiatric nurse Sharon Blautner starts to open up to him. But Bill is determined to continue his campaign, so he manages to get the unwitting Sharon to smuggle in an innocuous-looking package that's filled with the goodies he needs to engineer a spectacular escape. Naturally, Sharon's accused of complicity in Bill's escape and fired from her job. Even worse, she sees that Bill's appointed himself her personal avenging angel, meting out condign justice to the randy surgeon who liked his sex rougher than she did and to the sniveling bureaucrat who fired her as he warms up for the coup de grace: going after Edward Mackinnon, the treacherous onetime partner who stole Sharon's father's business and drove him to suicide--the same Edward Mackinnon who just happens to be the megabucks developer who plans to turn Carnegie-Hayden into a maximum security prison. Nothing of Mackinnon's, it seems, is safe from Bill's high-tech wizardry and homespun moralizing, and as Bill scores triumph after triumph over this robber baron, Sharon, who's working with the FBI, finds herself wondering whose side she's really on. The final payoff, though ingenious, isn't up to the rest of this exhilarating yarn from Hall (Nightmare Logic, not reviewed). But for most of its length, it really does manage to make its villain both scary and unsettlingly appealing.