SEATTLE (AP) _ In the beginning there is treachery. In the end there is reconciliation.

In between, Robert Schenkkan strip-mines the mythology of the American frontier in ''The Kentucky Cycle,'' one of the hottest pieces of new theater in the United States.

The nine plays, presented in two parts spanning six hours, trace the shifting fortunes of three intertwined families in the coalfields of the Cumberland Plateau from 1775 to 1975.

The fate of the Irish-Cherokee Rowens, white Talberts and black Biggses mirrors the devastation of a land once seemingly boundless in beauty and fertility.

The loss is not total, however.

Hardscrabble weeds and an occasional pine tree gain a toehold amid poisonous mine tailings and giant tree stumps. Joshua Rowen, the end of his family's line, throws over the boozing and corrupt profiteering that cost him his only son.

The premiere May 23 by Intiman Theater drew rave reviews. By the time it closes Saturday (commitments for the rest of the subscription season bar any extension), representatives of about two dozen other theaters will have seen the epic, said managing director Peter Davis.

''The Kennedy Center has been around and about, and two New York producers are flying in to see the show,'' said artistic director Elizabeth Huddle.

''Everybody's talking about it. They're all talking about bringing it to their theaters,'' Davis said. ''There really is a tremendous amount of national excitement.''

Schenkkan and stage director Warner Shook said there also was strong interest in a movie or television miniseries.

First, however, they would like to mount a production in London.

''I think it would do very well in London,'' Shook said. ''They love that kind of American roots production.''

The Fund for New American Plays of Washington, D.C., provided $125,000, the biggest grant ever made by the American Express-supported organization. Without it, the small company could not have afforded the production, Huddle and Davis said. As it is, the $750,000 expense amounts to more than a third of Intiman's $2 million season budget.

Tickets for each part range from $11.50 to $19.50. Patrons can see both parts in a handful of matinee-evening dates, on successive evenings or in more widely separated performances.

Even midweek shows at the 434-seat Playhouse have been selling out, and audiences often leap to a standing ovation at the conclusion, Huddle and Davis said.

''I've never received so many letter and phone calls from people who were so profoundly moved by anything we have done,'' Huddle said.

''It is kind of mythic ... both poetic and very hard-hitting. It just resonates back into the Greek tragedies and much of Shakespeare. It moves immediately into a conversation about what we are as a society.''

That's precisely the point, Schenkkan said.

''I would like to think that 'The Kentucky Cycle' is part of a quest for new meaning,'' Schenkkan said. ''People in the United States today feel a sense of drifting, being out of control.''

Appalachia and eastern Kentucky once were places where faith in America as a land of limitless opportunity and inexhaustible supplies of rich soil, clear water and fruitful forests first took root, Schenkkan said.

''We as Americans are less in touch with our history than many other people, and I think part of the reason is that myth of the frontier,'' he said. ''You cannot, sociologically or personally, escape your past. Without roots, you become rootless.''

Schenkkan, 38, was born in Chapel Hill, N.C., grew up in Austin, Texas, earned a bachelor's degree in drama with top honors at the University of Texas in 1975 and a master of fine arts degree at Cornell University in 1977, then began working as an actor in New York.

In 1984, while he was performing at the Actors Theater of Louisville, Ky., Schenkkan ran into an old friend who had worked for a time as a doctor in the southeast corner of the state, and he gave the playwright a tour of the region. The disparity of wealth and poverty was upsetting, but ''it was the juxtaposition of those landscapes'' - the devastation wrought by mining alongside untouched verdant hills and hollows - that really made Schenkkan angry.

Soon he was reading ''Night Comes to the Cumberlands,'' which focused national attention on Appalachia in 1963, and other works by Harry M. Caudill, a lawyer, historian and former Kentucky state representative.

Besides Caudill's ''passionate concern for the people and the land of the Cumberlands, he was concerned that the mistakes of the region not be repeated elsewhere,'' Schenkkan said.

Caudill committed suicide in November at age 68, probably without knowing what he had helped inspire.

Within a year after his visit to Kentucky, as a wedding present to his wife, Schenkkan wrote ''Tall Tales,'' set in 1890, eventually the sixth play in the series and the start of Part II. It was given a public reading at New Dramatists in New York and, after he moved to Los Angeles in 1986, at the Ensemble Theater there.

Twice he submitted it to Actors Theater in Louisville, but they passed on it, he said.

He continued to study the region, exploring other sources, finding ''acts of tremendous cruelty and tremendous generosity .. . a land so inherently dramatic and theatrical'' that he had to write more.

''I'd created this fictional family, and I decided, 'gee, it would really be interesting to follow this family,''' Schenkkan said.

After ''Tall Tales,'' he wrote the first play in the series, ''Masters of the Trade,'' set in 1775; No. 2, ''The Courtship of Morning Star,'' 1776; No. 3, ''The Homecoming,'' 1792; No. 4, ''Ties That Bind,'' 1819; No. 7, ''Fire in the Hole,'' 1920; No. 5, ''God's Great Supper,'' 1861; No. 8, ''Tablesalt and Greed,'' 1954; and No. 9, ''The War on Poverty,'' 1975.

By coincidence Shook and Schenkkan had the same agent in New York, Bill Craver, who sent Shook the script.

The first public reading of the full cycle was in 1989 over the course of three nights during the New Works Festival at the Mark Taper Forum in Los Angeles. Audience enthusiasm convinced Shook and Schenkkan that two longer parts would be better.

Mark Taper had the first option for the premiere, and copies were sent about 18 months ago to South Coast Repertory Theater in Costa Mesa, Calif., Old Globe Theater in San Diego and Intiman, where Shook had worked with Huddle as resident director.

''She was the one company that said yes,'' Shook said. ''It's daunting, you know. This thing arrives in the mail, and it's like the Manhattan phone directory.''

''They've hocked their entire season to do this play,'' Schenkkan said. ''It is a production which would tax, I think, any theater in the country.''

A decision on where to produce the show next probably will be made by the time it closes at Intiman, Huddle said. All that is certain now is that Intiman will not be co-producing.

''I'd love to, but we do not have the resources to do that,'' she said. ''I have to protect the company.''