That "After Hours" fails to satisfy, that it derails, that even its own director tires of the material halfway through, would disappoint no one if the name of Martin Scorsese didn't appear above the title. Anyone who loves movies loves Scorsese, the director of "Raging Bull," "Taxi Driver," and "Mean Streets"; expectations run so high that a movie like this, which admits its small ambition, inevitably falls short. What it offers, though, is a glimpse of an established artist at the height of his craft, yet as thrilled with the possibilities of the medium as a beginner.

Paul Hackett (Griffin Dunne), a word processor, meets Marcy (Rosanna Arquette) one night in a coffee shop. She tells him about her roommate Kiki (Linda Fiorentino), a sculptress who makes bagel-and-cream-cheese paperweights out of papier-mache', and gives him their phone number in Soho. Paul goes uptown, phones downtown, and thus begins the worst night of his life.

Everything goes wrong for Paul, and for those he touches -- he's like a Medusa who looks occasionally in the mirror, too. As long as Scorsese sticks with these three, the movie has a kind of dazzling creepiness, too close to reality to put at arm's length, too far to be comfortable. It's the work of a man who believes in nightmares, a tour de force of disorienting techniques -- slow motion, fast motion, jump cuts, time-lapse fades, stop-action montage, aerial shots, ground-level tracking shots, rapid dollies, close-ups that explode in your eye. For the first 40 minutes or so, there's not an unoriginal shot in it, or an unoriginal sound effect, either, but Scorsese isn't just showing off -- he's setting your nerves on fire.

And it's funny, too. Marcy, it turns out, is close to completely crazy, Paul close to completely normal, and their conversations are a jumble of rebuffs, missed connections and long pauses. They seem to exist in parallel universes, and Scorsese shoots them that way, in long takes, staring side by side into the camera. And he edits the pauses to measure, probing the connection between the aphasias of alienation and comic timing, between Beckett and Jack Benny.

It's the same connection he makes between affected indifference and deadpan clowning in the character of Kiki -- Fiorentino, with her square jaw and bassoon voice, slope-shouldered languorous in a black bra and leather skirt, gives her best performance yet. Scorsese paints her lovingly -- as a photographer of beautiful women, his only peer is Godard -- but he saves his camera's caresses, his cinematography's soft luminosity, for Arquette. (There is, in particular, one moment of erotic anticipation, when Scorsese loops swiftly to a close-up of her wink, that can knock you out of your chair.) Dolled up in a proper cotton shift, the wide-eyed, full-lipped Arquette is comic quicksilver in the role, snapping from cooing sexuality to giggling enthusiasm to sullen anger, and for no apparent reason -- her face changes at the clip of an MTV video, and Scorsese is plugged into her quirky rhythms, her nutty histrionics.

Dunne does his best work playing off Arquette. When he lies back and watches, furrowing the brow over his intense black eyes, he provides the exquisite puzzled counterpoint of a fine silent-era comedian; and when he tries to keep up with her, he looks like he's trying to catch a butterfly in his hands. But his character isn't filled in -- he's just Everyman, a figure for the audience to pour itself into. Scorsese sees Soho as a chamber of horrors peopled with pseudos and neurotics, and two cheers for that; but while he asserts a sort of moral superiority for Paul's "normal" life, he never tells us why we should agree. There's really no sense of what his life is like outside the nightmare.

On its deeper level, "After Hours" is about guilt, a familiar Scorsese theme; and as long as that guilt is attached to something real -- the sexual tension between Paul, Marcy and Kiki -- the movie stays moored, and unnerving. Much of what's wrong with "After Hours" stems from the loose, episodic script (by first-time screen writer Joseph Minion), which drops out Marcy and Kiki, only to add a subplot of mistaken identity (a neighborhood patrol thinks Paul's a burglar) that is faked, artificial -- an arbitrary device of farce. Late in the movie, Paul kneels in the street, raises his arms to the sky, and wonders, "What have I done? What have I done?" by which point you're thinking, "Well, what has he done?" instead of the mood of sexual guilt Scorsese captures earlier: "He must have done something."

Paul goes on to meet more Soho kooks -- a frustrated waitress with a bad dose of '60s nostalgia; a bartender; a Mister Softee vendor -- none as vivid as Marcy and her roommate. They're played, respectively, by Teri Garr, John Heard and Catherine O'Hara, all offbeat, versatile actors who seem oddly bland and routine. But the movie, by this point, has reeled out of control -- it's like being trapped in the morgue of Reader's Digest with a stack of "Most Memorable Characters I Have Known."

You've lost interest, and Scorsese has lost interest, too -- except for some running-in-the-street scenes in hommage to Fritz Lang's "M," the second half has little of the movie's early technical wizardry. He's good enough not to send you away hungry, though. The final scene finds Paul trapped in a papier-ma che' statue reminiscent of Edvard Munch's "The Scream," a neat recapitulation of an earlier idea; and under the closing credits, the camera zips around Paul's office as if it were mounted on a little boy's slot car. Still, "After Hours" isn't anything Scorsese can sink his teeth into. And Grandma, what big teeth you have.