Believing that a shadowy conspiracy offed JFK -- that Lee Harvey Oswald couldn't have acted alone, that dark forces beyond our ken manipulate reality on a regular basis and there's nothing we can do about it -- is as American as believing Elvis is alive and living in a trailer park or that Walt Disney is waiting to be resurrected from his cryogenic freezer. As Robert Stone's documentary Oswald's Ghost argues, it's as dark and potent a national myth -- a Rosetta Stone decoding late-20th-century cynicism -- as it is deeply misguided. With virtually no fresh territory left to cover on the JFK documentary front, Stone offers up a history not of the assassination, but of the many theories surrounding it. Dull but well-meaning, it neither adds to nor subtracts from that other Stone movie about JFK, but it's a necessary attempt.

Stone's meticulous archival research skills, displayed in 2004's superior Guerilla: The Patty Hearst Story, here benefit his early retelling of the assassination; there is quasi-revelatory video footage of Oswald's quasi-impromptu police station press conference, the sweatily articulate assassin carefully picking and choosing his denials. Stone reminds us that despite the popular compression of the assassination and its aftermath into an indeterminately quick time-frame, Oswald lived for two days before being killed by Jack Ruby. The Warren Commission's report didn't emerge for 10 months. When Oswald struck, the local reaction was disbelief: On Nov. 22, 1963, the Dallas Morning News ran a nasty ad accusing Kennedy of traitorously pandering to the Communists; how could one of his own be the one to fire, let alone, in historian Robert Dallek's words, "someone as inconsequential" as Oswald? How could an alleged lefty be the one to strike in a city full of people that wanted Kennedy dead?

The shift in public opinion from 1964's nearly universal acceptance of the Warren Commission's single-shooter verdict to 1967's nearly universal disbelief is traced to a number of sources. Conspiracy theorist Edward Jay Epstein argues in part that it was a zeitgeist thing: if you couldn't trust the government on Vietnam, what could you trust them on? Meanwhile, the inadequacy of Arlen Specter's much-derided "magic bullet" theory -- a single, fatal bullet with a near-impossible trajectory -- was fodder for writers like Mark Lane, whose 1966 tract Rush To Judgment opened the floodgates for more than 2,000 books, and as many variously plausible theories.

While exploring several of these theories with seeming neutrality, Stone is careful to pick a special bone with Jim Garrison, the hero of Oliver Stone's 1991 fever-dream: what that director forgot to tell us was that Garrison's prosecution of Clay Shaw might have had a lot to do with his generally overzealous prosecution of gays, and that the link between Shaw and Oswald was established by a nonsensical "decoding" method that owed its credibility to little more than arbitrary mathematics.

Between the archival footage and the talking heads (Dallek, Esptein and Lane are all on hand to offer up their ideas, joining other sideline players like Dan Rather), Stone lays out a decent if rarely compelling history; in the finale, he moves in for the kill. With no concrete evidence to disprove the Warren Commission's reports, it's up to the late Norman Mailer to sum up the case for the prosecution. Mailer essentially recaps Oswald's Tale, his meticulously researched 1995 biography in which he argues that Oswald -- a fringe media presence in support of Communism, as anyone tracking him pre-Nov. 22 could figure out -- was the assassin as career martyr, hoping for a trial in which to articulate his beliefs to an international audience. Was there a conspiracy? Quite possibly, but as Mailer sadly concludes, Oswald shot alone. Jack Ruby denied him -- and the rest of us -- a chance for calm reflection and conclusion about what it all meant.

Oswald's Ghost is a film in the public service, thanklessly attempting to put a stop to frenzied speculation after all these years. Why now is the question: Mailer finds it necessary to contextualize the assassination as the 9/11 of its day, reminding us how much our ideological battles and nation-defining traumas have shifted over the years. In its calm, dispassionate and stylistically enervated way, Ghost is a convincing film, but a dull one, raking open old sores for the still-suspicious.

The paranoiacs always get the best artists to stoke their flames; Oliver Stone's JFK may perpetrate an irresponsible myth, but it's also a great film. That its urge to impose order on the random is misguided is unfortunate; Oswald's Ghost argues convincingly for the necessary exorcism of such attempts, but that doesn't make its conclusions any more interesting to watch.