In the movies, it takes the heroes about two hours to track down and bring a serial killer to justice. In real life, however, things aren't that easy, as the true crime thriller Zodiac illustrates. An account of the most notorious unsolved mass murder in American history, Zodiac is an incredibly absorbing procedural, a chronicle of an investigation that took three steps backward for every one step forward. With the apt tagline of "There's more than one way to lose your life to a killer," this film isn't so much about the Zodiac himself as it is about how the men tasked with hunting him down became lost in a sea of obsession in the process.

July 4, 1969 -- a regular holiday night in Valencia, California -- until a young couple was shot in cold blood. Months later, the trigger man sent letters to three nearby newspapers, announcing his involvement not only in that shooting but also in a double-murder from the previous year's Christmas. With such an icy intelligence at work and a series of puzzling cyphers he wants published, the authorities quickly snap to attention and set about trying to capture the cold-hearted killer soon to be known as the Zodiac.

The film focuses upon three men in particular who become wrapped up in the hunt for the Zodiac: Robert Graysmith (Jake Gyllenhaal), a cartoonist for the San Francisco Chronicle who's drawn to the case by the Zodiac's symbol puzzles; Paul Avery (Robert Downey Jr.), a Chronicle reporter who soon becomes a potential target for the mysterious killer; and David Toschi (Mark Ruffalo), the homicide inspector at the head of the investigation. As the years progress, the hunt becomes laden with false leads, red herrings, and circumstantial evidence, driving those involved further and further into obsession, trying in vain to catch a killer who may very well have eluded their grasp.

Comparisons to Oliver Stone's JFK will definitely abound in discussions of Zodiac. Not having seen the former film, I can't say for sure how stylistically close the two are to one another, but from what I've read, both are multi-character, multi-layered dramas centered around a seemingly unsolvable mystery. This collective frustration shared by the various characters serves as the meat of Zodiac's complex plot, providing a backbone for the story's drama and driving the almost unbearable suspense.

Director David Fincher (returning to the movies after last helming 2002's crackerjack Panic Room) captures the feeling of a city on the edge, held virtually hostage by a single lunatic who claims murders he may not have committed, sends cryptic puzzles, and succeeds in messing with the minds of those trying to find him. Fincher's style is simple, but it contains a number of memorable shots (especially a fantastic shot of a fog-covered Golden Gate Bridge) and, most crucially, maintains an aura of suspense and dread, chillingly turning ordinary streets and sunny parks into the Zodiac's homicidal playgrounds.

James Vanderbilt's script follows a similar approach; the story itself seems uneventful, but the mounting number of obstacles that pop up during the hunt for the Zodiac build up more than enough tension to enrapture the viewer. Rarely before has a film that seems to have little actually happening come across as so thrilling and engaging, as the viewer's emotional investment in the characters and their situation is well rewarded with a number of scenes that will put you on the edge of your seat through the most subtle of ways.

Zodiac's "pins and needles" atmosphere is heightened by the terrific ensemble cast. Gyllenhaal gives a convincing performance as Graysmith, a slightly nerdy puzzlehound who, in the film's final act, finds himself as the only one dedicated enough to really sink into weeding out the Zodiac's identity. Ruffalo also delivers possibly his finest performance yet as the determined Toschi; you really feel his pain when he comes so close to landing some evidence on his Zodiac suspects, only to have some force sweep it all under the rug.

A number of other familiar faces pop up in brief but memorable roles, including Brian Cox, as a lawyer whose aid is seeked by the Zodiac, and Charles Fleischer, whose relatively brief apperance as a suspect is the most chilling in the entire film. I was a little disappointed, though, in Robert Downey Jr. Although he does fine work as the Chronicle's boozing star reporter, the script doesn't allow his side story to become as fleshed-out a part of the madness running rampant as it grants to the other characters.

True, with a story that's not exactly action-packed and a conclusion that most people already know, Zodiac does become a bit thin and weary at times. Still, this film does more with less than a lot of recent features. I think it's the best movie to reach cinema screens so far this year.

MY RATING: *** 1/2 (out of ****)

(Released by Paramount Pictures and rated "R" for strong killings, language, drug material, and brief sexual images.)