‘Quantum’ Leaps Into the J.F.K. Assassination : Television: On the season premiere tonight, Sam jumps into a script supporting the lone gunman theory.

John F. Kennedy is assassinated in Dallas again tonight. Only this time, the conspiracy is that there is no conspiracy.

“Everyone seems to be on the conspiracy bandwagon, but I’ve never been on it,” said Donald P. Bellisario, executive producer of “Quantum Leap,” which begins its fifth season with a two-hour re-examination of history at 8 tonight on NBC (Channels 4, 36 and 39).

“But I guess what really struck me the strongest was when my 12-year-old son went to see (Oliver Stone’s) ‘JFK’ and came home totally brainwashed by the film and started telling me all of these half-truths, falsehoods and speculation as if they were fact. And I decided if I could figure out a way to bring the tale closer to the truth--no one knows the truth and no one will probably ever know it precisely--but put forth another argument, another theory, another side to the story, that would be a good thing to do.”

So Bellisario wrote a script that leaps the time-traveling Sam Beckett into the Texas Book Depository building on the morning of Nov. 22, 1963--a script that firmly makes the case for Lee Harvey Oswald as the lone gunman and that breaks new ground for “Quantum Leap” by dealing for the first time with real historical figures and events.

On the “Quantum Leap” sound stage earlier this summer, an actor posing as Lee Harvey Oswald points an authentic Mannlicher-Carcano rifle--just like the one that the Warren Commission concluded Oswald used to kill Kennedy--out a fake movie-set window. Peering through the scope, he pulls the trigger and a loud shot echoes through the cavernous building. The actor cranks the rifle to eject the spent cartridge and chamber another, but the mechanism jams.

“Well, we just proved Oswald couldn’t have done it,” a member of the crew quips.

On take two, the gun jams again. Take three, same story.

“Kennedy lives,” cries another crew member.

On take four, the actor again struggles with the crank. For take five, he rapidly fires two shots but can’t get out the third. The company takes a break so that experts can fiddle with the gun.

Eventually, three shots ring out without a hitch. And even though Oswald only had one take, those shots on film provide proof, Bellisario contends, that if an actor who never fired a gun before could manipulate the old rifle, then Oswald--whom Bellisario portrays as an expert marksman--could easily have succeeded in killing Kennedy.

After reading several books on Oswald’s life and scouring the Warren Commission and other published accounts, Bellisario is a font of information about the assassination and the man who supposedly pulled the trigger. In an interview, he speaks in detail about bullet fragments, autopsies, X-rays, tape recordings, photographs, freeway entrances, the U2 spy plane and the logistics of the shot to support the lone gunman theory, while refuting many of the unanswered questions that conspiracy theorists use to advance the contrary view.

He even speaks of firsthand knowledge of Oswald--a chance Marine Corps meeting in 1959 that Bellisario includes in his script. Bellisario and Oswald both served in Marine air control squadrons and they were stationed, at different times, at a base in Tustin.

After completing his service, Bellisario went back to Tustin one day in early 1959 to visit some of his old buddies. There, he recalled, he began arguing with a Marine sitting on the floor in a supply shed who was reading some revolutionary newspaper.

“Here’s this Marine telling me something that I would expect to hear coming out of Radio Moscow, a whole load of communist doctrine,” Bellisario said. “I got incensed, and if you brought up something he didn’t like, he just kind of sneered at you. Finally I just walked away and I asked another Marine there, ‘What the hell is with this jerk?’ And he said, ‘Oh, he does that to everyone. He’s harmless.’ ”

(If there is a conspiracy, Bellisario offered in an aside, it was to cover up the fact that “a bunch of bureaucrats . . . screwed up and let somebody who should have caught the attention of everyone slide right through their fingers.”)

Bellisario’s brush with Oswald, coupled with having lived in Dallas for eight years in the late ‘60s and ‘70s, prompted him to take more than a casual interest in the minutia of the Kennedy assassination. But he said that he had mostly forgotten about it until his son and the younger members of his staff started preaching the merits of conspiracy after watching Stone’s movie.

But to advance his lone gunman theory within the confines of “Quantum Leap,” Bellisario had to break the one cardinal rule he had set for show. “The one thing you will never see us do,” Bellisario said when the series began, “is Dallas, Tex., Nov. 22, 1963.”

The show has had “brief kisses with history,” said Scott Bakula, who plays the time-traveling quantum physicist, but they have always been played for humor: He once met a 5-year-old Michael Jackson and on another occasion bumped into Dr. Heimlich, the man who created the Heimlich maneuver to save people from choking.

Bellisario said he originally decided to avoid known historical figures because most time-traveling literature has held to the belief that if you change known history, the ripple effect would bring on the apocalypse. But in writing this script, he figured out a way to change a bit of history along the way without altering the fact that Kennedy was assassinated--and therein lies the surprise of the episode and the reason for Sam’s leap to Dallas on that fateful day.

“I was a little surprised about his breaking the rules, but I sensed why he was doing it,” said Dean Stockwell, who plays Al, Sam’s holographic sidekick. “We’re going into our fifth season and instead of continuing on with the same old pattern, I think it’s the right time to give the audience something different. To add a new color. I think it was a wise idea.”

Bellisario said that he is also considering doing stories involving Marilyn Monroe, Elvis Presley and Richard Nixon.

But none of those promise to be as controversial as this. “Leapers,” as Bellisario affectionately calls the show’s devoted cadre of fans, are the kind of people who are fascinated by conspiracy theories, he said. He added that he has already received a good deal of mail urging him to expose the supposed conspiracy by showing that Sam, as Oswald, did not fire the fatal shot.

Conspiracy is firmly in vogue now, especially among younger people, Bellisario said, both because Americans are so mistrustful of and cynical about government and because “people don’t want to believe that, in one mad act, someone seemingly as weak and impotent as Lee Harvey Oswald could take out so vital and powerful a man as Jack Kennedy. It’s much easier to believe in legions of conspirators with millions of dollars to back it up.”

Bakula, who leaps in and out of portraying Oswald in five periods of Oswald’s life during the two-hour episode, believes that Bellisario’s steadfast point of view won’t disappoint even the most die-hard conspiracy buffs.

“I don’t think we will upset them,” said Bakula, who added that he favored some kind of conspiracy himself before shooting the episode and remains mostly confused even now. “The story is as much a strange journey for Sam and Al as it is a theory about what happened.”

“I’m not trying to dissuade anyone. I just want to show some other facts,” Bellisario concluded. “I admit that it would be popular to go the other way. It would be riding the crest of the wave to go the other way. But I don’t believe that is what happened and I just want people to take a look at the other side. And probably somebody will even say that is part of the conspiracy. I’m sure someone will find a way to identify some of my friends as spooks or something and then they’ll say I’m part of the conspiracy too.”