Sex, Lies, Videotape and Murder : MANHATTAN NOCTURNE.<i> By Colin Harrison (Crown: $24, 355 pp.)</i>

Lunchtime at Manhattan’s tres now restaurant, the Royalton, mess hall to the exalted. On hand are Larry King, William F. Buckley and Dan Quayle. “Almost everyone was rich or well-known in some way, and yet the dense celebrity of the room fostered a strange privacy,” writes Colin Harrison in “Manhattan Nocturne.”

Alone in this faux galaxy is Hobbs the media mogul, a big fat monster. An unflattering videotape of him has just been delivered to his chair. Hobbs snaps open a miniature video player at the table to watch this digital record of his most private vulnerabilities. Then he runs the tape through another machine.

“He turned the small piece of equipment around so that I could read the display. It said: ORIGINAL, NOT A COPY.”

This detail comes to us from the narrator of “Manhattan Nocturne,” a slightly celebrated New York newspaper columnist who discovers that a career--and life--he thought were sloping gently downward have suddenly pitched forward at a steep angle, pointing straight to hell.

Porter Wren suffers from a trinity of marvelous problems. One is the billionaire monster at lunch, Hobbs, a citizen Cyber-Kane. (He should try the bloodless corporate media types, by the way; they make Hobbs look like an earnest PBS documentary maker.) Another is the spectacular and sexy blond who seduces him. The third is a dead man, a brilliant and hip filmmaker who made the secret videotapes.

“Manhattan Nocturne” is a murder mystery dressed in fashionable urban noir, filled with erotic, funny and frightening riffs on New York, newspapers and men on the lip of middle age.

Our dissolute columnist is seduced by the blond into solving the murder of her husband, the filmmaker. Wren also is tasked, by the billionaire mogul, with uncovering a tormentor who possesses a deeply personal videotape.

How Wren manages to solve what seems to be a blackmail scheme and an unrelated murder--while not missing a deadline for his column--reminds me of a real-life newspaper sage who once shrugged off a plausibility snag in a front-page piece he was editing.

“Ah, well,” he said. “That’s why they call them stories.”

This one is told in the voice of Wren, who himself is a spiritual corpse deeply involved with the mystery behind a physical corpse. Wren claims he has limited his life to Just Getting By, based on two hard-won observations:

“The first was that my work had no useful function other than providing for my family. How could I believe that what I did had any importance? No one really learned anything, no one was wiser, no one was saved. Do newspapers even matter anymore?”

Despite this billboard of self-pitying despair, Wren commands the attentions, in the subsequent narrative, of the entire New York Police Department, the mayor (Rudolph Giuliani, in a hilarious cameo) and the aforementioned billionaire mogul.

But his gloom is broad enough to wrap the five boroughs.

“My second observation was that the degraded netting we identify as American urban civilization was in fact merely another form of nature itself: amoral, unpredictable, buzzing, florid, frenzied, terrifying. A place where men die the same useless deaths as did the tortoises and finches noted by Charles Darwin.”

An emotional carcass or a wise man?

“There was a time when I sought to use my limited skills to tell the stories of those who suffered unfairly or who were not worthy of the powers entrusted to them by the public,” Wren writes. “But these aims had been leached out of me (as they generally have been from the American news media, which, as the 20th century draws to a close, seems to sense its own clamoring irrelevance, its humble subservience to a pagan culture of celebrity).”

This dead soul, however, cannot rest in peace or stagnation:

“A newspaper column three times a week is a vulture that eats your liver away as fast as you can grow it back. You are chained to the rock, the bird approaches, eyes bright, beak stinking of its last meal, and alighting suddenly, it pecks and tears at the wound it abandoned two days before, eats its fill, gulping the pieces, and then flies away.”

True. But fortunately for Harrison’s fiction, the column is the least of Wren’s worries.

His real troubles begin when he pulls down the covers and slides into bed with the gorgeous blond who gave him the eye at a fancy party. For him, Caroline Crowley is the first episode of infidelity in a marriage that seems to be full-bodied in its satisfactions. Crowley is unforgettably beautiful, even as she becomes more chilling with every glimpse.

It is not until Wren’s second session in her bed, long after the breach of physical innocence, that we feel the wallop of Wren’s fall. She asks, he answers: about the birth of his kids, his wife, his fantasies and the sensation of loving a woman who has borne children as against one who has not. The intimacy is of a dimension way beyond sex, an excruciating treason.

It is often said that men bend toward affairs with women who strongly resemble their wives. (Quick, which one is Marla Maples and which is Ivana Trump?) Here, the woman has set upon cosmic twins. Columnist Wren is the pre-digital version of Crowley’s departed husband; like the newspaper man, the dead filmmaker was constantly scanning the horizon for stories with “wrinkles,” the odd twists that make tale-tellers giddy.

The dead man had secretly videotaped dozens of people, in slices and slabs of life that are brilliantly rendered by Harrison. Wren’s columns, aimed at capturing the same prey, seem hopelessly lead pencil next to the micro-technology of the hidden video cameras.

Following his infidelity, the spiral of the doomed Wren appears to accelerate when he receives a personal assignment from mogul Hobbs, the newspaper owner, to find the compromising videotape. When Wren balks, Hobbs reminds him: “Talent is cheap, Mr. Wren, yours included. You think you’re the only one who can tramp around some sad little scene and hack out the requisite dose of maudlin prose? Please, sir. Please! I can throw a bone in the street and get a newspaper staff.”

Gee, why does that passage stick with me?

Anyway, Wren is simultaneously on the trails of the tape and the murderer of the blond’s husband. Every person in the book exercises remorseless power over Wren, until, by diligent and ingenious reporting, he uncovers the place where both trails join and gains not only the upper hand, but a calm wisdom, too. Plus, he knocks a good 30-inch column out of it.

As the old newsman said, they do call them stories, after all. And “Manhattan Nocturne” is a very fine one.