No matter how you feel about it, a documentary about anti-Semitism isn't anybody's idea of a good time. But director Mark Levin ("Slam") pulled off an extraordinary feat: "Protocols of Zion" is an invigorating movie on a complex topic. Levin grants every side of the controversy equal screen time and still manages to come through loud and clear with his guardedly hopeful message: never stop believing that it is possible for people to overcome their differences and come together.

In the months after September 11, Levin kept coming across the following question: "Have you heard," people would ask him, "that no Jews died in the World Trade Center?" Levin, who is Jewish himself, decided to investigate. The trail of the conspiracy that supposedly warned all Jewish workers to stay at home on 9/11 led to "The Protocols of the Elders of Zion," a 19th century book that details plans for a secret Jewish cabal to rule the world. Even though the "Protocols" have been discredited as a fake circulated by anti-Semites for decades, they still sell, and they still have the power to convince.

In the best tradition of the Enlightenment, Levin's film takes the form of interviews and debates with anybody who has something to say about the topic: ranting street protesters who speak of Mayor "Jew-liani," inmates in a Federal prison, Kaballah scholars, polite neo-nazis, Jewish intellectual Douglas Rushkoff, Levin's own father, and the owner of the popular anti-Semitic web site "Jew Watch." In West Virginia, a skinhead sells black boots with swastikas and the SS insignia in the sole but doesn't wear them himself ("I'm more of an oxblood kind of guy.") During the Israel Day parade, blatantly racist Jews talk about Palestinians as "these people" and attack "deluded peace lovers" with as much venom as the skinheads have for them. Hasidic reggae rapper Matisyahu grooves at a Seder, and "Brooklyn born and bred" Palestinians react to the assassination of Sheik Yassin. Other passages concern Mel Gibson's "Passion of the Christ," the murder of Daniel Pearl, and Arabic TV mini-series that show Jews as scheming child-killers.

The result of the free-for-all approach is an impressionistic tour-de-force that's surprisingly entertaining. Levin knows that bigotry and hate cannot be opposed by more polemics; he doesn't hesitate to step in front of the camera and spar verbally with his interview subjects. By appearing as just another person with an opinion, Levin gives up some of his special powers as filmmaker, but the film is stronger for it. "Protocols of Zion" radiates the absolute faith that the rational humanist position is strong enough to withstand all lies and distortions. Levin gives the wing-nut bigots, tinfoil conspiracy freaks, and outright haters more than enough rope to hang themselves with.

The movie comes full circle with a coroner whose job it is to identify body parts from Ground Zero. Names, bone fragments, and the heartbreaking testimony of a 9/11 widow who had converted to Judaism for her husband provide the most horrible possible proof that Jews did in fact die in on September 11, 2001. What began as an investigation into the roots of a conspiracy theory ends as portrait of not just anti-Semitism, but humanity's endless capacity for hatred, fear, and misunderstanding.