The ""Nameless Detective"" (Nightshades, etc.)and Sharon McCone (Leave a Message for Willie) are both in San Diego to attend a private-eye convention. So the two San Francisco shamuses team up when Sharon's friend Elaine Picard--the chic, 40-ish head of security at the Casa Del Rey hotel--dies in a fall from a hotel tower. They soon uncover some offbeat happenings in and around the Case Del Rey: disappearing guests;the rocky homosexual relationship between the hotel's manager and his assistant. Moreover, it seems that Elaine--who had a rich, rightwing suitor--was involved in kinky doings down at a desert house called Les Club. And eventually, after two more murder-victims (a seedy private-eye/blackmailer, Elaine's therapist-friend Karyn Sugarman) are discovered, sleuth Sharon winds up at the isolated Les Club house--imprisoned by the murderer. . . but rescued by the Nameless. As in Pronzini's collaboration with Collin Wilcox (Twospot, 1978), there's surprisingly little fun in the double-shamus interplay here: the alternating narration provides only a hint of contrast (Muller writes very much like Pronzini, only less well); other than a bit of jealousy from the Nameless' girlfriend back in Frisco, the teaming-up situation generates no charm. Still, this is amiably entertaining fare for series fans--a cut below the better Nameless cases, perhaps, but a cut above the usual McCone level.