"FUTURE'S THIRD TIME IS CHARMING

Dear Mr. Einstein, By now you've seen Back to the Future parts I and II and you're eagerly awaiting the trilogy's conclusion.

You'll be happy to know your theory of relativity remains intact, although it might have been easier for you to demonstrate it had a DeLorean been at your disposal.

It also would have been helpful for you to have known what a jigawatt is, and how to produce 21-million of them. But your position in science is secured, while Dr. Emmett Brown (Christopher Lloyd) continues to toil in relative obscurity _ both now and in the future.

I suspect Back to the Future Part II confused you, even though your skills as a theoretician are legendary. Laws of physics do not apply readily to film making.

The sequel, you'll remember, was addled by numerous leaps forward and backward in time, horrid make-up effects and a convoluted premise involving parallel time planes.

Most annoying was its conclusion, which seemed to come midway in the adventure. It did. Part III wraps up Part II. In effect, Dr. Einstein, Back to the Future Part II served as a feature-length coming attraction for the series finale. (Not coincidentally, Part II makes its debut on videocassette today.)

Back to the Future Part III is an infinitely better picture than its predecessor. It's more coherent and streamlined. That's surprising, since parts II and III were filmed at the same time. Like all the films in the series, it was scripted by Bob Gale and directed by Robert Zemeckis.

This final segment has the innocence, energy and winning bravado of 1985's Back to the Future, which sent teen-ager Marty McFly (Michael J. Fox) to the 1950s to play Cupid to his mismatched parents. All Part III lacks is the light banter and the unpredictability of the original.

Most of Back to the Future Part III takes place in 1885, where Doc Brown is transported when his time-tripping DeLorean is struck by lightning. Marty travels back in time to save Doc, who otherwise will be shot by Buford "Mad Dog" Tannen (Thomas F. Wilson), a drooling ancestor of Marty's present-day nemesis, Biff.

This latest adventure wisely takes Fox's maturity into account; even he can't remain pubescent forever. References to high school and parents are practically non-existent.

Fox's Marty is more responsible. He's the one who reminds Doc that he can't change past events without affecting the future.

Unlike you, Dr. Einstein, Doc Brown is not coolly, scientifically dispassionate. He becomes smitten with Hill Valley's new schoolteacher, Clara Clayton (Mary Steenburgen), the only resident who has read Jules Verne and has been stirred by Verne's futuristic visions. As you might imagine, Doc is a bit of a futurist himself.

Doc's courtship of Clara is surprisingly sweet. For the first time in the series, Zemeckis gives adults dignity. They don't act like adolescents with gray hair.

Through means less precise than, say, your quantum theory of specific heat, director Zemeckis and screenwriting collaborator Gale have wrapped up the series. Yet, through a deft combination of storytelling and special effects, they've created a possibility for another sequel.

The visuals achieved in Back to the Future Part III approach Zemeckis' Who Framed Roger Rabbit. Yet they're not overwhelming. The concentration remains on character.

The acting, Dr. Einstein, is first-rate. At this point, Fox and Lloyd wear their characters like a second skin. Steenburgen is a little flat; it takes a certain degree of aplomb to balance the energy emanating from Lloyd's 1,000-jigawatt Doc Brown.

Incidentally, Doc thanks you for your unified field theory. Without a single set of laws explaining gravitation, electromagnetism and subatomic phenomena, Doc's DeLorean might as well be a snowmobile.

Yours in time,

Hal Lipper.

MOVIE REVIEW

Back to the Future Part III

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Director: Robert Zemeckis

Cast: Michael J. Fox, Christopher Lloyd, Mary Steenburgen, Thomas F. Wilson, Lea Thompson

Screenplay: Bob Gale, based on a story by Zemeckis and Gale

Rating: PG

Running time: 120 minutes

Excellent +++++; Very good ++++;

Good +++; Mediocre ++; Poor +