This wouldn't be a good time to accuse the networks of fluffmongering and spinelessness in prime time, at least where TV movies are concerned. Less than two months into the new season, there've already been sobering, venturesome dramatic treatments of such subjects as wife abuse ("The Burning Bed"), heart attack and brain damage ("Heartsounds"), teen-age suicide ("Silence of the Heart") and the traumatic effects of violent crime ("Victims for Victims").

You couldn't call this sissy television. Nor were these movies mere weepers of the old candy-coated terminal-illness school. In each case, something was said. Questions were asked.

Now comes yet another grim and rewarding ordeal: NBC's four-hour, two-part adaptation of the Joe McGinniss book "Fatal Vision," about the dauntless nine-year struggle of a mother and father to obtain justice in the vicious murder of their daughter and two granddaughters. The man finally convicted of the crime was their son-in-law, ex-Green Beret and well-liked Army doctor Jeffrey MacDonald.

The film airs tonight and tomorrow at 9 on Channel 4. It's another of television's conscientious nightmares, as absorbing and disturbing as it ought to be, and it is more than a case history of a monstrous crime. "Fatal Vision" has themes and implications that nag and disturb. The operative cliche' would appear to be "dark side of the American dream," but the dream here is really a universal one and the darkness as fundamental and disquieting as the compulsion to destroy.

Written by John Gay and directed by David Greene ("Friendly Fire"), one of the few TV-movie directors who might plausibly be called brilliant, "Fatal Vision" opens on a rainy night at Fort Bragg, N.C. in 1970. From his home, MacDonald is breathlessly phoning for help; his pregnant wife, Colette, and his two little girls -- Kimberly, 5, and Kristen, 2 -- lie stabbed and bludgeoned to death. He later tells military police that his home was invaded by a murderous "hippie" cult similar to the Manson family. Eventually that tale is shattered by the evidence presented in court.

It's an "eventually" slow in coming for the mother and stepfather of the slain woman, played by Eva Marie Saint and Karl Malden, memorably teamed as supporting players three decades ago in "On the Waterfront." Gay's script doesn't give Saint much to do beyond watching and worrying, but Malden is splendid as the dogged investigating Freddy Kassab. You look past the grotesque-resplendent shnoz and what you see in Malden's eyes is riveting and unassailable conviction.

At first both parents believe their son-in-law's story; the alternative seems unthinkable. Flashbacks establish that outwardly this was a happy snapshot of a young family, though in several scenes Colette looks distracted, anxious. Questioned after the killings by Army interrogators, MacDonald says, reasonably it appears, "No one ever had as good a life as I had. What the hell would I want to wreck it for?" After an Army tribunal has cleared him, MacDonald goes on to lead a rather frantically womanizing but otherwise exemplary life. As an emergency-room doctor in San Diego, where he has transplanted himself, he's beloved. Says a grateful cop to him after MacDonald patches up a wounded comrade, "God bless you, Doc, you're one in a million." He's given a good-luck party when he goes off to a new trial.

But from within the cultivated sang-froid emerge telltale signs of obsessive paranoia. MacDonald refers to those investigating for the Army as "idiots," "sleazy jerks," sees them all as conspirators, and after an early hearing gleefully tells Kassab, "Hey, did you see the TV coverage? We're going to get really good press. Just terrific." Now even murderers are wise in the ways of media. Months after the killings, when he was still being presumed innocent and wrongfully harassed, MacDonald appeared on the Dick Cavett show (a talk-show host is seen but not identified as Cavett in the film) posing as a personable victim of Army persecution.

MacDonald is played by a young actor, a discovery, named Gary Cole, who looks like a slightly beefier Kristoffer Tabori and whose face suggests the boyish cunning of Tom Brokaw. Cole knows just how much diabolical Hyde to expose from within this ingenuous Jekyll. The filmmakers may make MacDonald's attorney, played by Barry Newman, a touch too Hollywoody (he behaves like an agent), but Gary Grubbs contributes a compellingly understated deadpan as the young Raleigh, N.C., attorney who prosecuted MacDonald when the case finally came to trial in 1979.

Obviously there was the potential to turn sensational material into lurid material, but Greene and Gay cannot be faulted on that. The NBC promotion department can; it has circulated for advance consumption the grisliest scenes from the film, the reenactment of the murders. This is a man murdering his wife and children, not really the stuff to send out for use on "The CBS Morning News" and "Entertainment Tonight."

It's in the third hour of the film that the murders, as the evidence suggests they occurred, are reenacted in flashback. A medical examiner is explaining to Kassab that the diverse blood types of the victims enable him to retrace the killer's actions. As he talks, the night of the killing is shown, silent except for the narrator's voice. The camera zooms in chillingly on the A's, B's and AB's that represent blood types on a map of the house.

When the speculative account of the murders is finished, Malden breaks down and weeps. It's the first time the character sheds tears on camera. The film has been made conscientiously enough so that we can see what is ugly and a little frightening in the parents' pursuit of the case as well as the horror-next-door nature of the murders themselves. And we can see what is disarming in the facade maintained by MacDonald. The film wouldn't work if the viewer didn't find him at some points an attractive figure. As portrayed here, he's your average go-getting Joe, the fellow down the block. He hasn't a lot of faults, really. Except that he slaughtered his wife and children.

A case that abounds in ironies has been given an added one, or two, by the NBC broadcast of the film. According to author McGinniss, who did not collaborate on the screenplay but did serve as a paid consultant to the production, lawyers for MacDonald, who is seeking a retrial, wrote two letters to NBC in an attempt to discourage the production. McGinniss says no legal action was threatened but the NBC promotion department has tried to exploit the situation by telling viewers in promos that this is the movie "some people don't want you to see."

It has also been reported that MacDonald himself, regardless of the protests of his lawyers, stands to profit from the telecast of the film, but McGinniss says reports of the amount MacDonald will receive have been exaggerated. McGinniss says NBC paid $130,000 for the dramatic rights to "Fatal Vision" but that the sum was not paid to him. By contractual stipulation, 75 per cent of that money went to Dell, the firm that was originally going to publish the book. McGinniss had a falling-out with Dell and took the book to Putnam, but the dramatic rights remained Dell's to sell.

Of the remaining 25 percent of the $130,000, McGinniss says 40 per cent goes to MacDonald -- roughly $13,000. "That's not nearly as glamorous as the figures CBS was throwing around," says McGinniss. "The CBS Morning News" reported last week that the payment in which MacDonald shared was $200,000 and implied he got a sizable portion of that. However, MacDonald does continue to profit from sales of the book. McGinniss estimates he has been paid $93,000 since the contracts were signed. MacDonald enlisted McGinniss to write the book in 1979 because he thought it would help exonerate him.

"I'd be happier if he had never gotten anything," McGinniss says. "All these arrangements were made in the summer of 1979 when I was completely open about his guilt or innocence." McGinniss is asked if he feels morally uncomfortable with the fact that he has helped finance MacDonald's ongoing defense. "He's paid a high price for whatever he's received," McGinniss says. "He would just as soon the whole thing with the book never happened." And McGinniss feels the book enabled people to find out what really occurred on that February night in 1970 when all hell broke loose inside a man's head.

Of the NBC production, McGinniss says, "The film is factually faithful to the book, and I have no serious complaints." However, he confesses he is not thrilled with the portrayal of him that is included in Part 2 of the movie. "I was the one who urged that they eliminate that character entirely, on the grounds that it's completely superfluous. It's one of many pieces of my advice that they didn't take," McGinniss says.

"In truth," adds McGinniss, "I did not sit around with my jaw hanging open and take three steps backward every time something significant happened" the way Frank Dent, who plays him, does.

As "The Burning Bed" did earlier this season on NBC, "Fatal Vision" has a tendency to unravel during the trial scenes, which dominate the final hour. One may feel that either much more or much less of the trial should have been depicted. And Greene basically wastes Andy Griffith in the part of Justice Department lawyer Victor Worheide, the kind of role Griffith has played too many times before. Greene and writer Gay may have been hindered by the NBC legal department's nervous mandate for slavish factual accuracy. It gave them little leeway for a dramatic production, but they managed.

Considerable advance publicity and the sensational nature of the story being told may guarantee a sizable tune-in for the film. Encouragingly, the filmmakers seem less concerned with manipulating the narrative in order to keep an audience hooked through the commercials than with their storytelling instincts and an honest desire to present the material in a way that demands attention. There is little blatant maneuvering to make this "easy" for an audience.

The same was true with such films as "Silence of the Heart" and the more recent "Victims for Victims" and in fact viewers by the multimillions stayed with those films. The 18.8 rating and 28 share for "Victims" was a very good showing for such a grim subject, particularly since it was slotted against one of the few big-draw NFL games of the season. NBC Research estimates 28 million people saw all or part of it. CBS Research estimates that 30 million saw all or part of "Silence of the Heart." The network's TV movie about teen-age suicide earned a 21.9 rating and 35 per cent share of the viewing audience, making it the fifth-ranked prime-time show for the week ending Nov. 4. Maybe it's not like they're tuning in for "Hamlet" out there in Television Land, but the increasingly serious TV movie has proven itself in the public arena. Anything that encourages one more "Heartsounds" and one less "Ellis Island" is commendable.

This season, some of television's darkest hours have also been some of its brightest. "Fatal Vision" qualifies on both counts. It's a stunning confrontation with the eternal question, "Why?"