In the '60s and '70s, some political movie thrillers tried to look like TV news programs. Now TV news programs sometimes try to look like political movie thrillers. Tonight's edition of the promising but flawed "Frontline" series of documentaries on public television opens with footage of a massacre in North Carolina, while the show's zippy, mock-urgent theme music plays behind it.

On last week's premiere of the series, "An Unauthorized History of the NFL," at least some of the portentous musical punctuation sounded like it came from the soundtrack of the movie thriller "Taxi Driver," John Hinckley's favorite flick.

Such touches, glitzy and hypey--the ABC's of television news, they might be called--don't help the credibility of the report, but they do make it more vivid, electric, adrenal. And perhaps more watchable for a general audience, though it would seem that the basic material of "88 Seconds in Greensboro," tonight's "Frontline"--at 8 on Channels 26 and 32--is explosive enough.

In 1979, five people were murdered on the streets of Greensboro, N.C., as they protested the activities there of the Ku Klux Klan. Six Klansmen and Nazis were subsequently acquitted of the crimes, although a federal grand jury will soon meet to consider charges of civil rights violations. That justice has yet to be served seems obvious--TV news cameras were on the site and videotaped the killings--but the "Frontline" program examines the possibility, already raised by others, that the police were not only incredibly negligent in this case, but may actually have been in collusion with the Klansmen.

The question is raised and probed by reporter James Reston Jr. and producer William Cran, but it is not really answered. The program concentrates on the role played in the tragedy by Edward Dawson, a paid police informant at the time of the shootings, present at the scene of the violence, and yet never called as a witness during the subsequent trial. Dawson now appears to be persona non grata both with the police department that once paid him for his information (as well as the FBI, whose role is not made clear) and the Klan that he infiltrated. According to one observer in this report, it was Dawson who urged Klansmen to carry rifles to the scene of what became a sickening massacre.

Unfortunately, Dawson looks to be a plum candidate for exploitation by either side; his veracity could always be impugned later. As he admits to Reston, he was charged with and imprisoned for desertion during World War II. He designed a virulently racist poster used to inflame Klansmen prior to the shootings. For Reston and Cran to make him the pivotal figure in the case may have been an error.

Dawson does say at one point, apparently of the Klan, "These are a bunch of half-wits that got themselves into a jam." The same might as justifiably have been said of the Klan's victims, members of the Communist Workers Party; that their cause and tactics hardly elicit one's sympathy may partly explain why this news story seems to have been underplayed by the national press (a student at Columbia University stood up on the most recent "ABC News Viewpoint" program to accuse "the media" of being part of a general conspiracy to suppress it).

In harrowing footage of the event, we see and hear the wife of one slain protester responding to his death by shouting, "Long live the Communist Workers Party!" This motto was even placed on a tombstone. Earlier, we hear members of the CWP say that brown lung, a disease afflicting some of the textile workers they tried to organize in North Carolina, is not just a job hazard that ought to be dealt with by employers, but a sign and symbol of the corruption of capitalism. It is hard not to entertain the thought that, at least in the abstract, some of these zealots welcomed the opportunity to appear to be martyrs.

That hardly mitigates the outrage of what happened that day or of what was apparently gross negligence by local police. "The police could have stopped the massacre," Reston says conclusively at the end of the report. This edition of "Frontline" has its faults, but it is a gripping confrontation with a shameful day that should not be allowed to fade away with yesterday's newsprint. It becomes most lacerating when we see a videotape made for court use of a woman TV reporter who witnessed the murders and recalls the scene under hypnosis. She weeps and remembers, "I just wanted them to stop shooting," and this description is intercut with footage made of the incident.

Unlike some of the techniques used in "Frontline," this one seems an incisive use of television that makes a real-life nightmare come horribly alive again.