Private-eye Alo Nudger of St. Louis (Buyer Beware, 1976)is hired by comely Jeanette Boyington to find the man who killed her twin sister Jenine. Jeanette's theory? That Jeanine was murdered by one of the men she met by making blind-dates on the kinky ""nightlines""--telephone connections made, late at night, when both parties call certain unused phone-company numbers. Furthermore, the same psycho seems to have killed several other nightlines users too, in the same bathtub/slashing style. So Nudger, despite some oddly violent interference from Jeanette's snooty mother, sets out to trap the killer: vengeful Jeanette makes phone-dates via the nightlines; Nudger tails these suspects, checking to see if they match the killer-clues (blond hair, big hands). Meanwhile, as yet another bathtub slashing is reported, Nudger's own testing of the nightlines leads him into a delicate phone-friendship with a suicidal woman named Claudia. And by the time Nudger corners one psycho-killer and exposes another one, he has come face-to-face with Claudia--falling in love, learning her dark secrets (a fatal-child-abuse conviction), and saving her from yet another suicide-try. The mystery-windup here is close to half-baked, with some dippy motivations and one all-too-obvious twist; Lutz's hard-boiled prose occasionally goes pulpy. (""Nudger's soul was a thousand pounds of cold lead. . ."") But most of the way through this is a taut, lean shamus-diversion--edged with rueful humor, Nudger's not-so-tough character (a nervous stomach), and the surprisingly touching Claudia romance.