Zodiac is The Good Shepherd of crime thrillers. Robert DeNiro's prolix spy movie from 2006 starred Matt Damon as one of the CIA's founding spooks. Well-crafted, it left viewers cold. David Fincher's nearly three-hour film about the serial killer who terrorized Californians in the late 1960s and '70s is meticulously wrought and left this viewer in a perplexed sweat.

To call Zodiac a glorified police procedural is reductive and not completely accurate since the typical example ends with a bust and, quite often, conviction or acquittal. The director of Se7en and Fight Club isn't in a position to offer a satisfying narrative conclusion, let alone justice. Fincher does offer a highly discomfiting experience, using a polished technique and first-rate actors, more likely to be a critical darling than a crowd-pleaser. The insolvable puzzle is both gripping and frustrating in its inconclusiveness. Posteriors will be numbed but minds will be engaged.  

Based on two books by San Francisco Chronicle cartoonist Robert Graysmith, it begins in 1969 and ends in 1991. Graysmith (Jake Gyllenhall) was working at the paper when the self-named Zodiac killer wrote to the editors taking credit for a pair of recent murders and insisting a cipher that would reveal his identity be printed on the front page. The movie focuses on Graysmith and two others who became obsessed with solving the intermittent crime spree -- the Chronicle's crime reporter Paul Avery (Robert Downey, Jr.) and fabled city detective Dave Toschi (Mark Ruffalo).

With the objectivity and dispassion of a good reporter, Fincher -- who grew up in the Bay area -- vividly conveys the fear that gripped the entire state. The crimes themselves are depicted in a handful of tense scenes containing violence that falls somewhere between graphic and restrained. Police investigations are mounted in San Fran and two small nearby jurisdictions in the region, and the trail also leads to Southern California. Avery, a hard-partying man of the era colorfully limned by Downey Jr., puts his journalistic reputation on the line pursuing the killer. Ruffalo does a superior job in the role of Inspector Toschi, the real-life model for Dirty Harry, who was unable to solve the single murder that took place in the city. 

Scant progress is made on any of the crimes. If indeed a single individual was responsible (three different actors play the perpetrator, who's always partially concealed), he wasn't very efficient or prolific. He claimed thirteen victims, but the police counted seven, five of whom died so he may have taken credit for phantom crimes. Fincher excels at teasing out certain implications of the case. The Zodiac manipulated the media along with the police and obviously craved attention; he was arguably the first serial killer of the information age and the authorities didn't have many of the technological tools we take for granted today. 

Once the trail went cold, amateur code-breaker Graysmith decided to write a book in which he would solve the crime and the last third of the movie traces his efforts. Fincher's challenge was to make researching a book, poring over old case files, and analyzing handwriting samples and a few fingerprints seem exciting. The energy he wrings out of Graysmith's increasingly frantic obsession is hard to sustain due to the facts and the long timeline. As sure-handed as Zodiac is in most respects, it feels like Fincher strains to add intricacy and density. He clearly relishes embarking on a journey with Graysmith and the audience -- sniffing out clues, offering red herrings and venturing into blind alleys.

As the case fizzles out, the movie appears to contort itself. A primary suspect emerges -- Arthur Leigh Allen (John Carroll Lynch) -- but Fincher undercuts that suspicion and intentionally confuses the issue. He successfully transmits the frustrations and tedium of police work. Viewers gain an appreciation for the reality that crime-solving is not as easy or glamorous as it's usually made to seem. So much so that they may yearn for the surety of a renegade cop like Dirty Harry. 

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