Multiplication Fable : LAUGHING DOG A Leo Bloodworth and Serendipity Dahlquist Novel<i> by Dick Lochte (Arbor House / William Morrow: $19.95, 395 pp.) </i>

Dick Lochte is a generous mystery writer. In this one book, he gives us two detectives, two major plots (and countless minor ones) at least half a dozen bizarre murders, more villains than a reader can keep track of, two jaunts overseas, one to Italy, one to England, an elaborate game of “Trivial Pursuit” (old movies division)--and twice as many pages as the average mystery novel.

Lochte introduced 14-year-old Serendipity Dahlquist of Beverly Hills, and her out-of-shape, down-at-heel, 50-ish retired-police-officer-turned-private-eye partner Leo Bloodworth in his 1985 book, “Sleeping Dog.”

The notion of a sassy, sandy little girl teaming up to solve a crime with a worn-out old law enforcement type worked well for Charles Portis in “True Grit,” and Lochte evidently felt it was time to update the idea.

In “Sleeping Dog,” someone had made off with Serendipity’s dog, and she hired Leo Bloodworth to find it, with such ensuing merry high jinks as the brutal, senseless decapitation of the little girl’s beloved pet, and a climax at a rock concert in a grotesque amusement park where more characters drop dead than in the last act of “Hamlet.”

In “Laughing Dog,” a young man from New Orleans hires the team to find his young runaway sister Cece, and an aging television superstar wants back some emerald earrings stolen by a young lover. A profusion of comically inept but horrific criminals stand in the way at every turn.

Along with a selfless generosity with his material, Lochte has a gift for grotesquerie. Whatever page he opens the book to, the reader can count on meeting at least two nasty characters (often homosexuals), tricked out in high-camp costumes and hair styles, driving outlandish vehicles, and drinking opium-laced cocktails in surroundings that would shame the creator of “The Cabinet of Dr. Caligari.”

This is the sort of detective novel known as a light-hearted romp. It is meant to make us laugh. Most of the cast open their mouths only to utter scathing wisecracks. Almost every figure in this story--good, bad, woman, child--is contemptuous of everyone and everything apart from his or her self. Lochte plainly finds this sour approach to life endlessly diverting.

Serendipity’s grown-up observations on matters we’re not accustomed to hearing about from little girls ask a lot of the reader. Now and then, Lochte remembers to make her a real child, with a real child’s innocence and capacity to misunderstand adult matters--but too rarely. Most of the time she is sophisticated beyond her years, and this finally erases whatever charm she started out with.

Among many other locales that he manages to make repulsive, Lochte in this book takes us into a Hollywood where every producer, actor, director, agent, writer, and best boy not only dresses funny but is a monster of depravity of one kind or another--or of several kinds at once.

Sex for hire, sexual enslavement, porn and kiddie porn, drugs, theft, conspiracy, betrayal, cruelty to animals, and casual murder on the weakest pretext, seem in this book the essence of the motion picture and television industry. They also seem to Lochte the essence of hilarity.

One of his characters is a skinny little kid called Slide, who has been a pederast’s kept boy for a prosperous while, but now is back running errands for cheap drug dealers. Lochte’s Bloodworth and Dahlquist deride Slide for needing a bath. Even his secondhand motorcycle, which he uses to help them rescue one of their clients, comes in for sneers.

Lochte is an intelligent, playful, knowledgeable writer, but in “Laughing Dog” as in “Sleeping Dog” before it, his ruthless quest for laughs suggests a chilling lack of sympathy for the human condition.