Fully realized characters, complex plots and excellent writing are the qualities that attract readers to Valin's series about Harry Stoner, private eye. In his eighth appearance, Stoner describes his assignment to find missing Ira Lessing, a businessman from Cincinnati, Ohio, beloved for his generous help to troubled teens. The detective is with Lessing's childlike wife Janey, and his partner, Len Trumaine, when they learn that Lessing's body has been discovered, brutally beaten. A punk teenager, Terry Carnova, not only confesses but boasts of killing Lessing, but Stoner isn't convinced. Terry's pathetic lover Kitty insists the murderer is ``Tommy T,'' a male hustler who caters to masochists. With this information, the detective gropes his way through the fog that shrouds the facts about the victim and several suspects in the case. The story stands as a ``mainstream'' novel as well as a fine mystery. Mystery Book Club alternate. (Mar.)