This is a story about a pair of autistic twin boys and their family.

"Maybe," Larry Roof, the boy's father once told a friend, "maybe if there had been just one, it might have been different, but with two . . ."

But there were two, so the story changed -- and is still changing -- taking on elements of heroic legend and becoming, in its scope, sweeping, maybe even cosmic.

Larry Roof is a gnat, buzzing the giant American institutions of banking and real estate. He is David, out to do battle with the Goliaths of state (in this case, South Carolina) and federal bureaucracies. Or with traditional medicine. Or with traditional social work.Or with traditional hat-in-hand charitable organizations.

The twins, Shannon and Shawn, are now 14. They do not talk. They communicate almost exclusively by what their father calls, "tantruming." When the boys were 4, they were diagnosed as hopelessly retarded and brain-damaged. Larry and Phyllis Roof were advised to institutionalize them. This they found, simply, unacceptable.

They took a big risk. A recent HEW publication quotes child psychiatrist Donald J. Cohen, a specialist in autism, on this point:

"Parents are usually unhappy, worried, angry, discouraged and exhausted. But they are not, as a group, unconcerned or unloving . . . (when the children are kept at home) marital strife, separation outcomes" because of the "impossible stress" placed on a marriage.

And Dr. Cohen was talking about one autistic child.

The twins' behavior, the Roofs felt, never exactly fit the image of severe retardation. As Phyllis Roof recalls, "So many times they would outmaneuver us, figure out locks on doors, how to get over a fence." But it wasn't until they were about 9 years old that autism was suggested.

"That was the first time we had a feeling of real hope," says Phyllis Roof.

Their hope for their own boys and a gradually broadening dream of providing hope to other parents of similarly afflicted children, led the Roofs to the second part of their story: Sparkleberry School, "Mr. Leon" and 112 prime forest acres called Corley Woods Farm. Also banks, mortgages and foreclosures. And perhaps a breakthrough in new ways of financing "nonprofit" ventures: in profitable partnership with corporate America.

The Roofs live near Columbia, S.C., in the county Larry Roof, who is 42, grew up in. The diagnosis of autism led them to explore the techniques for communicating, almost all of which are controversial to some degree. There was a good, but incomplete, experience with the Columbia Program for Autistic Children. They were trained in the Judevine method, basically a behavorial-conditioning regimen which is higly controversial, but often, as with Shawn and Shannon, dramatically effective.

From this was born the idea of a school. Behaviorally-disabled children -- the description Larry Roof prefers -- require, they believe strongly, 24-hour consistent care. The Roofs were thinking in terms of a farm.

"The peaceful qualities of the farm and forest are, in themselves, regenerative," says Roof, who notices that a walk in the woods "can touch a peacefulness -- an inner quality" in his sons and other similarly afflicted children. "That's why we believe land is so important, but in the minds of some people, it's a waste of good land."

Almost as though it were destined, the couple learned that a friend of Roof's, lumberman Leon Corley ("one of the last authentic folk persons in South Carolina") had a farm to sell.

Against all traditional business advice, the Corley family maintained the loan on the property so that the Roofs and their nonprofit Sparkleberry School (named for the indigenous shrub) could purchase it with a minimum down payment. (For which the Roofs sold their home, remortgaged some other property and established the popular Sparkleberry Folk Fairs).

The loan is due today. And, the Roofs expect, today will mark the beginning of foreclosure proceedings.

"They'll want to start cutting down those big trees," says Larry Roof.

Money has always been the problem. The competition between nonprofit groups for the always too-little federal and state funds available is as vicious as one might envision among starving groups scrapping over the last morsel of food.

The historical farm (site of the 1781 Battle of Tarrer Springs) in Lexington County, with its 19th-century farmhouse, has some of the oldest and largest pine trees left in South Carolina and is one of the most rapidly developing areas in the Southeast.

The Corley family always resisted development, although the farm is a developer's dream.

Of course it is the Roof's dream too.

The one thing virtually all "experts on autism can agree on is that nobody knows exactly what it is, or exactly what causes it. In the 1940s and into the '50s, one widely accepted notion was that it was caused by parental coldness to the child, laying an appalling guilt on already suffering parents. That theory has now been thoroughly discounted, but there are still only theories about its causes and almost no agreement on its treatment.

There is, however, better knowledge about what autism is. There is a lot of evidence pointing to a disturbance, perhaps chemical, in the part of the brain which sorts out external stimuli into separate sensations. The autistic child, authorities now feel, is bombarded by a cacaphony of sounds, colors, visions, all unfiltered, unsorted, at once totally bewildering and deeply threatening. It may cause a complete withdrawal, or it may provoke seemingly meaningless actions.

A child who howls may simply be trying to drown out the bombardment of sounds from without. A child who flinches from his mother's caress may be feeling the caress as searing pain. Autism's basis symptom, the HEW booklet quotes Dr. Cohen as saying, is "the inability to relate to people and social situations in a normal way."

The Roof twins were beautiful babies and easy to care for. "Everybody thought they were little girls," recalls Phyllis Roof, now 40. "They were adorable." They did not have the typical autistic behavior characteristics.

As they grew older, however, they became more difficult. Like most 7- or 8-year-olds they loved to run around on their own, play, get into mischief. But, of course, there are still no communication. The older they grew, the harder it became for the Roofs and for their daughter, Dee, now 17. Both parents express deep regret at the strain on their daughter "because we were making the choices we were."

But, says Phyllis Roof, "I think she understands now. She's away at school and she just grooves on the social life there. . ."

Once the Roofs adopted the Judevine techniques, they saw what they term 100 percent improvement in the twins' behavior. There is a kind of communication for the first time. With eye contact they had not achieved before, and with techniques to counter the recurrent tantrums (soothing words, stroking), the Roofs are focusing their efforts more strongly on turning Sparkleberry School on Corley Woods Farm into a reality.

Both Roofs are former teachers (she, English; he, art). "That made us concerned about the needs of all special children," says Roof, "and the way they are treated."

Roof, who has degrees in art, architecture and theater design, quit his job to concentrate full time on seeking ways to finance the school, to find consultants on new therapies, to raise money, design projects, to interest corporations. The Roofs live on Phyllis Roof's salary as an executive secretary at a local hospital.

Associate Russ Rustard, who is helping publicize the project, calls Roof "a genius in conceptional design." Among his plans are solar greenhouses to provide food for the school, produce for sale and the raw materials for research in nutrition and behavior. The farm would provide the environment "to which special children generally respond with trust and curiosity," says Roof.

Because a good section of the farm is highway frontage, a potential commercial goldmine, Roof conceives profitmaking businesses -- such as a restaurant -- in partnership with a major firm (which would provide seed money and reap profits, with a continuing benefit to the school). Campbell Soup is reviewing a restaurant concept and "hasn't said no yet." A large computer corporation has been approached for technology in a language lab.

"It would be a dynamite program," says Rustad. "It's there if only the right people could listen . . . an alternative to traditional institutions.

Rustad and the Roofs have traveled the country seeking advocates, contributors, anyone who would listen. They are candid in their search for media attention and their time is running out. There will be lawyers, of course, to fend off the foreclosure, but so far there is still no solid commitment.

There is a forthcoming Hollywood benefit which the Roofs hope to share with a California organization for handicapped children. There are promises, hopes and the Roofs refuse to show discouragement.

"We don't intend to lose it," Larry Roof said this week. "We haven't put in this much to lose it."

Shawn and Shannon are handsome teen-agers. There is no distinct sign that there is anything wrong. Sometimes this can make things tricky. Once, recalls Larry Roof, he brought them to one of the Sparkleberry Folk Festival benefits he has staged.

"The man taking the tickets held out his hand as the boys entered. Shannon reached out, pulled off the man's spectacles and flung them across the room. The poor man was so shocked . . ."

The twins are also strong and healthy. This is also trickly. "They have an amazing speed of decision-making," says Larry Roof. "They'll take advantage of any distraction, and what do you do when one runs away? I had to decide whether to have one in my hand or two running loose. The first time I decided one should run with me while I chased the other. But he decided not to run and dropped to the ground like an anchor. That's the kind of double-teaming they're so good at."

"Sure, there strains," says Phyllis Roof. "But even with it all, they bring a great deal of joy to our lives, the feeling that we can help them, get through, so they can achieve the level they can is so satisfying . . ."

"Sometimes it is like living in a pressure cooker," says Larry Roof, "standing with head against wall, saying, 'What day is it? What do I do next?' But we keep going because we really believe that a first-class approach to helping the behaviorally handicapped -- rather than giving them the land that nobody wants -- could produce miracles."

Queries about Sparkleberry may be addressed to J. Larry Roof, 2110 Leaphart, Rd., W. Columbia, S.C. 29169.