THERE ARE so many chilling moments in "Father Cares: The Last of Jonestown," that the 90-minute radio documentary from National Public Radio becomes a flash of insight into the malignant character of the Rev. Jim Jones -- the man who in November 1978 led 913 men, women and children to mass suicide in Guyana. The show, to be broadcast locally on WAMU-FM Thursday at 9 p.m., is drawn from 900 hours of tapes uncovered at the People's Temple and chronicles the last months of Jones and his followers. The tapes have never been broadcast in the United States.

In a program filled with terror, no moment is as harrowing as when the increasingly obsessed Jones goads his faithful followers into describing how they would deal with "defector" relatives.

"An 8-year-old boy had suggested killing his mother, cutting her up and poisoning the pieces and then feeding the bits to his remaining relatives. To that, the Bishop's laugh trilled uncontrollably from bass to contralto prestissimo for an endless set of measures. There was no joy in the percussive offensive sound, only triumph and bloodlust, as he contemplated the poisonous feast. The laugh hung high in the air, like a contagious ether." That's how James Reston Jr., who created and wrote the radio script, describes the scene in his new book on Jones, "Our Father Who Art in Hell." As heard on the tape, it is one of the most frightening segments ever broadcast.

"Father Cares" allows the listener, as Reston says, "to look directly into the experience, to feel the slavery of the followers and the power and sacrilege of Jim Jones." The founder of the People's Temple was convinced of his place in history and consequently made sure that his thoughts and sermons were meticulously recorded.

Within days of the tragedy, the 971 tapes found in Jonestown had been flown out by the FBI in a bodybag and Reston spent more than a year trying to gain access to them under the Freedom of Information Act. In January 1980, Attorney General Benjamin Civiletti personally intervened, ordering a compromise wherein all but 25 of the tapes released (the exceptions relating to Larry Layton and the attack on Rep. Leo Ryan; Layton goes on trial next month for his role in the killings at the airport in Guyana).

Bootleg tapes of the final suicide ritual have been in circulation since shortly after Jonestown occurred, but "Father Cares" does not use them. For the book, Reston had to organize the tapes, establishing their chronology (they were mostly undated), choosing representative moments. "The tapes were beyond description," Reston has said, "authentic evil, equintessential evil, a return to bestiality. What Joseph Conrad had begun in his novel 'Heart of Darkness,' Jones ended.

"That was a great feast for the novelistic eye," Reston says of the tapes, which form the basis for his book as well as the radio documentary. "I was able to reproduce authentic interchanges. Up until this time, it had all been second-hand accounts through the eyes of surviviors. And while I would like to think I'm a good enough writer [to capture the nuances and tones of the tapes], there's just an enormous difference between reading cold print and hearing the authentic thing."

When Reston first conceived of doing the radio program, he called upon NPR president Frank Mankiewicz, with whom he had worked on the David Frost Watergate project. On a Saturday morning last summer, as silent and somewhat stunned NPR brass listened to two hours of Jonestown tapes; the project was on.

"Father Cares" makes no pretense of telling the whole Jonestown story, or even providing an overview; it is essentially a portrait of Jones. He began his charismatic ministry in Indiana in the mid-'50s, attracting the poor, the displaced and the disenfranchised with a fiery nondenominational evangelism that cast Jones as the atheist savior figure. After migrating to the San Francisco area in 1963 -- followed by his congregation -- Jones rose to political power before being accused of financial and sexual abuses. In 1976, he moved almost a thousand people from "Babylon" to what he considered Utopia -- the socialist experiment and agricultural project in Guyana that became Jonestown.

The first half hour of "Father Cares" telescopes those early years in San Francisco (where Jones had the largest Protestant congregation in California) and the initial move to Guyana. There, "his people would finally be alone with the night and his voice," those hours of greatest fear and intimidation when Jones would fly into paroxysms of paranoia and his followers would abandon rational behavior and profess their willingness to die for him.

There's the reverse brainwashing, with Jones trying to replace his zealots' rote responses with less obvious slogans for the benefit of visitors: "You call me Jim, don't say Father or Dad . . . say we, never say Family." And the program passes through the many White Night rehearsals years before the final step was taken: "Who the hell wouldn't be ready for a White Night? Only I'd like for one to come and not pass . . ." These scenes are particularly affecting, for as Reston says, Jones "had sentenced them and then suspended the sentence, waiting for the glorious moment."

And always, without end, one hears Jones, excoriating his people, draining their will, their free choice, exhausting their resources, "trivializing the malignant destiny that waited." The language is raw for radio, but the virulence of the emotions behind the words is even more staggering. In the last 60 minutes, as the pace quickens, as the tape segments grow longer, one senses the real mystery of "Father Cares" and why NPR chose not to run excerpts from the suicide tape. "It's really not the story that is being told," Reston points out. "If the program works," adds the show's producer, Deborah Amos, "you will be with them at the end.

"There's not many things you do in your professional career where you have to think about good and evil," says Amos. "It's the most powerful tape I have ever touched in my life and I will never, ever in my career have another piece of tape like this."

Amos and engineer Skip Pizzi spent hundreds of hours listening to the tapes, trying to pinpoint the most telling moments, clearing up tape hiss (though many of the tapes were of outstanding stereo quality), deciding what direction to take the story. At the time, Pizzi was working with some engineering trainees and, Amos recalls, "one night I came out of the studio and the master control man said 'Do you understand what's happening to those trainees?' I said no. 'Well, my office is where they drop off before they go home. It's detox for Jonestown, they come in and talk to me about it . . . and they're very sad when they get to me.'

"I cried one time," Amos admits. "And then I got angry that [Jones] could still do that . . . and I was surprised because I've never had that reaction to tape." The scene Amos cried over involved an older black woman who testifies to Jones that "when they hurt you, they hurt me. I tell you the truth, I'm not going to lie. You're the only father I have. You're the only family I have. I give my brothers to you . . ." The woman then breaks into a heartfelt gospel-style testimonial: "All the days of my life ever since I was born/I never heard a man like this man before . . ."

After a verse, the congregation claps hands and joins in the revival atmosphere, but in the end, it's Jones himself who dominates the song, shouting out praise to his own power, pushing his captive audience into a frenzied Indian-type howl, what Reston describes as "the shrill yelps of terror as they slapped their mouths, pursed in a halo of righteousnes, the righteousness of the hunted . . . the savage staccato screams of a thousand carried out into the black immensity.

"This broadcast will take Jonestown through the highest emotional level in this country that there has ever been," Reston says. Because "Father Cares" is such a troubling program, a number a member stations have declined to carry it. NPR, seeking to control the consequences of "Father Cares," will follow the broadcast with an hour-long panel discussion and national call-in led by Bill Moyers and featuring psychiatrist Robert Jay Lifton and theologian Janathan Z. Smith, who consider Jonestown one of the most significant events in the history of religion."We felt we had a responsibility to bring [the audience] down a little easy." says Amos.

"People are making a mistake if they feel that Jonestown was a cult; it was a religion and nobody's dealing with it. Theologians are terrified and intellectuals cannot deal with it. We don't know what the magic was, what the symbols were, the structure of it. And we'll never know until we know what happened in the jungle."