Zodiac **** out of ****

A masterpiece

A smart, engrossing, exhaustive trip through the investigation of a serial killer, "Zodiac" gets first-ballot election to the hall of definitive crime pictures.

It's a movie of shadows, noise and gunfire. It's about those nights when each grain of sand on a gravel road makes its own sound under the weight of a black Mustang. The movie embodies the intoxicating, bewildering, constant threat of murder, a phenomenon unique to a community invaded by a serial predator.

Even Nebraskans have been touched by it: If you were a 6-year-old living in Omaha in 1983, you knew the artist's composite of the man who killed those two boys before you ever heard the name John Joubert. Yesterday I looked up Joubert's sketch online and saw those doe-like, alien eyes more than twice the size of his mouth, all under a blue ribbed stocking cap. I had nightmares about that drawing, about being snatched off the sidewalk and dumped in a ditch. Safety stickers went on windows. The FBI rolled into town and invaded our milk cartons. Kids stopped walking to school.

That's the mood of "Zodiac." Its fuse may burn for almost three hours, but it must. James Vanderbilt's screenplay, based on Robert Graysmith's book, spans 15 years, and it ends with no one behind bars. Yet Graysmith's writing and director David Fincher's dreamy, elegant visuals, tightly grasp the moment and the obsession of the men hunting for San Francisco's most famous serial killer.

Fincher opens the movie with the Zodiac's third and fourth known victims: a married woman and one of her misters parked on a lover's lane in Vallejo, Calif. Not long after this murder, he starts writing letters to the local newspapers, including the San Francisco Chronicle, where columnist Paul Avery (Robert Downey Jr.) spearheads the coverage, while cartoonist Graysmith (Jake Gyllenhaal) lurks around the editorial conversations on how to cover the murders and how to help catch the murderer.

Graysmith - divorced, nerdy and awkward - slowly evolves into the movie's key catalyst. He observes as the Zodiac leaves cryptograms concealing messages, courts the media, inspires false confessions and floods the two homicide cops assigned to his case, Dave Toschi (Mark Ruffalo) and Bill Armstrong (Anthony Edwards), with phony claims and leads. By the movie's final hour, Graysmith alone is pursuing the case with a zeal that costs him his family.

The investigation, carried out over several years and split into three acts, is too dense and rich to explain in a review. What Fincher conveys is the pleasurable enormity of it.

Like a novel, "Zodiac" sprawls out and revels in tiny details. It loves the names of places. It cares about whether the Zodiac killer wrote his "k" with two strokes or three. It's fascinated with the guy who knows a guy. It appreciates the trickiness of warrants. And it has the right - because it's unsolved - and the guts to sincerely invest in red herrings. It's about the pursuit of truth, not the revelation of it.

The ensemble cast snugly fits into this story. Gyllenhaal may not be the ideal actor to play Graysmith - he's almost too wide-eyed - but he finds the right notes in the movie's final hour, when it's Graysmith's show. As Toschi, Ruffalo creates a man who inspired Steve McQueen's "Bullitt:" thick, tough, clever and clearly fond of haberdasheries. Edwards does a nice turn as the forthright partner. Downey, in one of his better recent performances, makes the writer Avery into a smart, cocky reporter chasing Hunter S. Thompson's lifestyle a little too passionately. When he crosses the line, he does it for the right reasons but gets burned by his ego and addictions. Dermot Mulroney, Philip Baker Hall, Brian Cox, Donal Logue and other actors play it completely straight in their supporting roles and play straight very well.

And then there's John Carroll Lynch, who plays a prime suspect, Arthur Leigh Allen. He has only a few scenes, but they count. If you want to see a creep, watch this performance.

"Zodiac" is Fincher's most polished, mature work. "Se7en" might be a centerpiece of any 30-something's movie collection and "Fight Club" is, for all its absurdity, memorable pop culture. But "Zodiac" mixes Hitchcock and 1970s paranoia dramas without gunning the gas pedal, like Spike Lee's overwrought, unhinged "Summer of Sam." Fincher subtracts the flash of previous works to add cohesive professionalism.

The movie has a certain, almost plastic sheen on it. The murders seem surreal and stage-like, cribbing from Errol Morris' famous documentary "A Thin Blue Line" and feeling like a Flannery O'Connor short story, when dread, violence and the Almighty converge for blood judgment. "Zodiac" is ordinary enough to be unsettling and twisted enough to be compelling. It will be long forgotten for the 2008 Oscar season, but it's the craftiest, best film of the early year.