One of the talkiest recent Bagby cases begins when Jack Sterling--a former underworld stool-pigeon--turns up dead: this ""sitting duck"" had recently returned to N.Y., and narrator-sleuth Bagby was among the first to spot him. But was revenge the murder? The stabbed body is found on black satin sheets with a whip nearby, suggesting a sex crime. Furthermore, Sterling had been living with one hefty woman and bar-hopping with another. . . and both women (or are they perhaps transvestites?) have disappeared. So the Bagby/Inspector Schmidt inquiries focus on the women as well as Sterling's old enemies--in a plodding mini-puzzle with none of the humor and appealing characterization that have enlivened some of the past few Bagbies.