Aseveryone knows by now, Oliver Stone’s incendiary docudrama JFK locates the American heart of darkness in a conspiracy to assassinate John F. Kennedy — a shadowy right-wing cabal that, according to Stone, encompassed the CIA, the FBI, the vice president, and a paranoid subculture of Southern anti-Communist fanatics. Stone’s theories about how and why this conspiracy unfolded are fairly insidious, for he has little compunction about inventing details. When he demonstrates the unlikelihood of the ”magic bullet” theory — the Warren Commission’s hard-to-swallow finding that a single bullet caused a total of seven wounds in Kennedy and Texas Governor John Connally — he’s on solid ground. But when he flashes an image of some anonymous operative actually planting the bullet on a hospital stretcher, it’s just an overheated act of conjecture. Yet Stone’s instincts as a filmmaker transcend his glibness as a moral inquisitor. The JFK assassination has a built-in pull (just listening to the theories is like getting sucked into a whirlpool), and the tabloid ”revelations” laid out by JFK are feverishly immediate. If Stone hasn’t exactly solved the Kennedy assassination, he has captured — with a dark cinematic flair that leaves you reeling — why it still looms like a sickening nightmare.

The killing of John F. Kennedy haunts us for two vastly different reasons. When that final bullet blasted open Kennedy’s brain, in some dread-ridden way it almost seemed as if America itself had killed the President. Regardless of who (or how many whos) pulled the trigger, the simple fact that a leader so beloved could be struck down with such incongruous horror told us that we weren’t the nation we thought we were, that beneath our lingering postwar optimism lay demons and madness.

But the assassination also haunts us perceptually. Our fascination with the tragedy might have faded long ago were it not for the 8 mm home movie shot that day in Dealey Plaza by dress manufacturer Abraham Zapruder. Without that footage, we wouldn’t expect to know who killed Kennedy; it would all seem distant, hopeless, part of the pre-media-culture past. But because of the Zapruder film, which allows us, visually, to relive the assassination, we feel as if we should have the answer, as if the clues were right before us, waiting to yield the truth. The essential mystery of the JFK assassination — not simply the welter of facts we don’t know, but the very fact that we can never know — is at the heart of our obsession with the events of Nov. 22, 1963. That day disturbs our dreams because it seems to exist in some netherworld at the dawn of the media age. That day mocks our desire for certainty. It tells us that even in an era when everything is recorded, the more we see the less we know.

This, far more than any cooked-up, all-encompassing conspiracy theory, is the true subject of JFK. The movie is about the way we see the assassination, about the way it lives inside our minds. Stone keeps returning to that day in Dallas. He creates a spectacular layered effect, interpolating bits of the Zapruder film with a half-dozen styles of grainy staged footage, each with its own distinctive ”reality.” Parts of JFK play like a documentary we’ve miraculously entered. Stone weaves such a heady tapestry of detail-fleeting interviews with bystanders; pinpoint analyses of how many bullets could have been fired, and from where; shots of the street, of the grassy knoll, of people waiting for Kennedy to arrive (after a while, we start to recognize them) — that we feel as if we’re right there, on that day. Stone turns the assassination into a purely existential event, and that makes its horror all the greater. The atmosphere of impotence and invisible doom — the sense of a nation about to crack open — is overwhelming.

All of which leads to the question …who done it? Stone has framed JFK as a classic cover-up thriller, like Z or All the President’s Men. His hero is New Orleans district attorney Jim Garrison (Kevin Costner), who in the mid-’60s came to believe that Lee Harvey Oswald had links to a local anti-Castro cult and, as a result, launched a savvy but reckless inquiry into the assassination. The real Garrison was a cocky troublemaker who, many say, had a way of coming up with theories and bending the facts to fit them. Stone turns him into a white knight, with Costner doing a Southern-gentleman variation on Eliot Ness. This Garrison, though, isn’t really meant to be a three-dimensional figure. In JFK, he’s our guide through the jungle — through the cascade of witnesses, flashbacks, and voluminous information that Stone compresses into a dizzying stream of consciousness.

The movie unfolds on twin dramatic tiers. There are the Dealey Plaza scenes, which pass by in a kind of floating technological dream. And there is Garrison’s investigation into the kinky right-wing subculture of New Orleans, where he pursues the leads of such characters as the hairless mercenary pilot David Ferrie (Joe Pesci) and the suavely effete businessman Clay Shaw (Tommy Lee Jones). Curiously, the movie never really makes a connection between the two levels. When Garrison, desperate to get his evidence heard in public, puts Shaw on trial, viewers may wonder what, exactly, Shaw is being accused of. Knowing Lee Harvey Oswald? Being a member of the CIA? (That hardly connects him to JFK.)

The plot doesn’t really make sense; it’s just a dramatic frame on which Stone can hang the various conspiracy theories. Yet when it comes to dramatizing those theories (the proverbial what-might-have-been), his filmmaking is so supple and alive, his obsession with the visual aspect of history so electrifying, that JFK practically roots itself in your imagination. The movie’s most dramatic moment is Garrison’s replaying in court of the Zapruder film. For this is what every Kennedy-assassination conspiracy theory — and, indeed, Stone’s movie — finally comes down to: a man riding in a car, struck by a bullet, his head shooting off to the left (hence a second gunman aiming from the knoll). Beneath its labyrinthine paranoia, JFK says: Here was the true tragedy of Nov. 22, 1963 — the day America stopped believing its own eyes. A-