The unnerving tale of Al Smith, a Fort Lauderdale police detective who went undercover as a hit man for hire, as told by crime writer McDonald (Blue Truth, 1991). What terrifies here is the repeated verification of the old saw about the banality of evil. In one memorable case, a sweet, petite, under-20 blond, answering an ad placed in the personals by a love-hungry bachelor, makes a request for the murder of her husband; short of cash, she wants to finance the crime on the installment plan. In another, a stockbroker wants his wife fed to the alligators and makes a down payment on the killing with his credit card. While Smith is one steely cop--a big, burly Vietnam vet--the arrests he makes can leave him unsettled or worse: As McDonald remarks in typical tough-guy prose, ``When you put yourself...in a cop's no-man's land, the feelings leave scar tissue across your memories.'' Hard-core scenes--one involving a Colombian-Mafia turf war, and another a tension-filled encounter between Smith and some real hit men in a pancake house--come as a relief: Here, everything is as it should be, with good guys and bad guys clearly delineated. Too many cases piled atop one another, and some ill-advised digressions--Smith's early romps with women shed no light on him or his profession--but, overall, a gripper with an appalling premise: that your next-door neighbor, the one with the cute dimples and the angelic demeanor, just may be Smith's next client.