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TomDillard/Dallas MorningNews/Corbis
Lee Harvey Oswald is escorted by Dallas Police Department officials after his arrest Nov. 22, 1963.
"Oswald's Ghost" (PBS, WGBH Educational Foundation, rated TV-PG, $24.99)

"Oswald's Ghost" is an elegantly crafted, 90-minute obituary for the conspiracy theories surrounding the assassination of President John F. Kennedy.

On the one hand, filmmaker Robert Stone (no relation to Oliver) reports that about 70 percent of Americans still disbelieve the official investigation into Kennedy's killing. Veteran conspiracy jockey Mark Lane crows that, unlike the major networks and editorial boards of The Washington Post and The New York Times, "I have been right all along" about the plot to kill Kennedy.

But a more impressive roster of experts, including the late Norman Mailer, Priscilla MacMillan and Todd Gitlin, has arrived at a different conclusion. Edward Jay Epstein, who has criticized the official Warren Report on the assassination, now thinks there was no anti-JFK conspiracy. "As we cover decade after decade, not a shred has come out that would indicate what this conspiracy was," Epstein says. "After 40 years, none of the theories pan out."

I don't know what Stone's agenda was in making "Oswald's Ghost." I understood it as a fairly subtle commentary on time. If there had been more truths to reveal about the Kennedy assassination, time would have yielded them. But it didn't. To borrow the language of "The X-Files," popcult's greatest conspiracy homage of recent time: Maybe the truth was out there all along.

Why is this relevant? Because we again are awash in conspiracy theories. Every major news event attracts an accompanying backwash of debunking, counter-factual argument and conspiracy-mongering. A recent Vanity Fair reported that "many people in London" believe that Prince Philip headed up a conspiracy to kill his erstwhile daughter-in-law, Princess Diana. Really? As if anyone cared.

The main event in contemporary conspiracy-mongering is, of course, 9/11. A few weeks into the fall of 2001, a friend called me from France and urged me to be the first American journalist to report the "truth" about the Sept. 11 attacks. He then sent me French newspaper stories "proving" that no airplane ever crashed into the Pentagon. While it is true that my French isn't what it used to be, I wasn't convinced.

The French have not monopolized this version of events. Not infrequently, I receive e-mails with subject lines like, "Yes, the Bush/Cheney regime deliberately let 9/11 happen."

"The Pentagon was struck by a 'hijacked' airliner 45 minutes after two other 'hijacked' airliners struck the WTC," this recent missive continued, "without the airliner being intercepted, approached, chased, or even seen by our air defenses? The Gov't still refuses to release clear video of whatever happened at the Pentagon to this day, six years later??? Why???"

This e-mail urges you and me to visit the Web site 911truth.org, and all I can say is, feel free to exercise your First Amendment rights. There is a "truth novel" (paging Mr. Orwell) about 9/11 coming out from a "New York Times Best-Selling Author" later this month. Look for it! On the Web site, you can check out the "peer-reviewed" Journal of 9/11 Studies. The site also allows you to download "resistance music," like Zan Overall's "I Want to Believe You, Mr. President," sung by Bill Horn and 911Truth Chorus. Sample lyric: "The more I learn about 9/11/Believing you gets harder to do."

You can watch clips of "Boston Tea Party" for 9/11 truth at the Web site boston911truth.org. I saw a video of retired Brigham Young University physicist Steven Jones explaining that he had found chemical evidence of Thermate, "a high-tech incendiary that melts steel like a hot knife through butter" in World Trade Center detritus. A press release from architect Richard Gage announces that "the official explanation of the total destruction of the World Trade Center skyscrapers has explicitly failed to address the massive evidence for explosive demolition."

Are there mysteries? Yes, there are mysteries. A friend of mine thinks that American Airlines's Flight 587, which crashed in Queens in the fall of 2001, was shoe-bombed. (Shoe bomber Richard Reid was arrested a month later on an American Airlines flight.) Even though I have since met an engineer who consulted on the investigation, which attributed the crash to wake turbulence and pilot error, I think my friend may be right.

But I don't think Dick Cheney, or the titans of capital, or the agents of the Apocalypse blew up the World Trade Center and killed 3,000 people to further some dark cause. I think the plot was hatched right where we think it was, in the faraway, hot sands of anti-American hatred.

I doubt the truth is out there. I think it is already here.

(DVD special features: A visit to Dealey Plaza in Dallas, "The Zapruder Film and Beyond" and an interview with producer Robert Stone. The DVD is available for purchase at www.shoppbs.org and proceeds support public television.)

Alex Beam is a Boston Globe columnist