A most inappropriate Thanksgiving attraction, "Halloween," arrives at a time when reports of an authentic horror story are bound to accentuate the triviality of a mere horror movie.

Not that this plodding exercise in sham apprehension would look impressive even if one felt starved for morbid stimulation. Now at area theaters, "Halloween" is far more proficient at torpor than terror.

Evidently conceived as a genre talent showcase by 30-year-old John Carpenter, who also collaborated on the minimal scenario and composed the undernourished score. "Halloween" is a stab at a derivative minor classic. It's apparent where Carpenter got his horror devices - and a minor misfortune that he hasn't been able to synthesize them in a fresh or exciting way.

The movie begins with a prologue in which a teen-age girl is stabbed to death in her room on Halloween night, 1963. The murder is depicted subjectively, supposedly from the point of view of the killer, who peeps at the girl as she necks with her boyfriend, extracts a butcher knife (inevitably reminiscent of the murder weapon in "Psycho") from a kitchen drawer, climbs a steep staircase (inevitably reminiscent of a key setting from "Psycho") and attacks the victim, who is unclothed and appears to recognize her assailant.

In a moment it's revealed why she knows him: the killer is the victim's kid brother, dressed in a clown's costume. This kicker is the sort of "masterstroke" that makes the crime itself look clownishly implausible, but Carpenter blunders on. It's 15 years later, Halloween Eve, 1978. Two passengers in a car navigating through a rainstorm (inevitably reminiscent of a situation in "Psycho") are entrusted with cryptic expository lines updating the murderer's case history.

The passengers are a psychiatrist, played by Donald Pleasence, and a nurse. According to the physician, the killer was a child of six when he stabbed his sister and has failed to respond to treatment while growing up in an institution for the criminally insane. He is convinced that this bad seed, named Michael, will always be a menace - indeed, the essence of evil. He is determined to impress this fear on a parole board scheduled to review Michael's case.

Arriving at the institution to pick up Michael, doctor and nurse discover that he's been waiting for them. In fact, he steals the car from under their negligent noses and heads for the scene of the crime, Haddonfield, Ill., an idyllic small town obvioulsy chosen to duplicate Hitchcock's use of pretty, serene Santa Rosa, Calif., as a backdrop for terro in "Shadow of a Doubt."

Once back home, the grown Michael, whose face remains averted from the camera, branches out a bit, recalling sources other than Hitchcock. He begins stalking potential victims derived from Brian DePalma's "Carrie" - high school girls played by Jamie Lee Curtis. P. J. Soles and Nancy Loomis - and affecting a heavy mockasthmatic wheeze borrowed from the maniac played by Ross Martin in Blake Edwards' "Experiment in Terror."

Since there is precious little character or plot development to pass the time between stalking sequences, one tends to wish the killer would get on with it. Presumably, Carpenter imagines he's building up spinetingling anticipation, but his techniques are so transparent and laborious that the result is attemuation rather than tension.

Carpenter lacks the stylistic flair and psychological penetration that have allowed De Palma and George Romero to contribute new classics to the horror in recent years. Carpenter's scenario isn't rooted in anything except old movies, and it develops too arbitrarily to establish roots even in that shallow ground.

Michael's case history doesn't sustain the movie beyond the prologue. The killer has no identity as a dangerously demented human being. He's a thing lurking in the dark, the bogeyman that a neighborhood kid takes him to be.

Moreover, that darkness is so Stygian that it's often impossible to discern anyone's face or appreciate the monster's unexpected entrances. The murky images are the closest Carpenter comes to giving the picture a "look," and it turns out to be a self-defeating one, similar to the lighting miscalculations that seem to be plaguing many movies these days, especially "Comes a Horseman" and the still unreleased "September 30, 1955," both shot-by Gordon Willis and both literally lost in the dark for long, long stretches.

Eventually, Carpenter's dimly perceived bogeyman degenerates into a bad joke. After snuffing the high school girls played by Soles (who appeared in "Carrie" as the best pal of bad girl Nancy Allen) and Lomis - whose promiscuity apparently renders them expendable - Michael is confronted by the straight-arrow character of Janet Leigh and Tony Curtis but more suggestive of a melancholy, ungainly young Lauren Bacall).

The movie ends with the sound of heavy, heavy breathing still haunting the pleasant tree-lined streets of Haddonfield. A horror melodrama that resorts to an "irony" like that obviously wants to be congratuled for digging its own grave. Congratulations.