Killer instincts

David Fincher’s Zodiac has a lot going for it, and it gets even better once you realize that this is something different, something less tortuous and more reflective, from the director of Seven, Fight Club and Panic Room. Unfortunately, when all is said and done, none of that matters quite as much as it should.

The unsolved mystery of “Zodiac,” the serial killer who terrorized California in the 1970s, necessarily remains so in Fincher’s film, which chiefly concentrates on the struggles of the investigators most involved in the case. Foremost among these are police detective David Toschi (Mark Ruffalo), San Francisco Chronicle crime reporter Paul Avery (Robert Downey Jr.), and Robert Graysmith (Jake Gyllenhaal), the Chronicle cartoonist who became obsessed with the case and ended up writing two books about it.

Fincher and screenwriter James Vanderbilt begin with the initial Zodiac killings in 1969, then settle in with an elaborately detailed account of the investigations that unfolded in various Bay Area police departments and in the offices of the Chronicle. The grisly killings at the outset suggest a horror film/mystery thriller, but it’s soon evident that much of the central action will be in the methodical police procedural mode, augmented with streaks of docudrama and glancing character study. All of which proves conclusively inconclusive, in ways that are both liability and virtue for the film as a whole.

In its earnest (and faintly morbid) realism, Zodiac is a sharp-eyed evocation of California in the 1970s and a haunting portrayal of the heavy toll taken on the most persistent investigators of a sensational and increasingly complex murder case that goes unsolved. And it also seems to be putting a canny reverse spin on an earlier “Zodiac” movie, Dirty Harry (1971) with Clint Eastwood, which is referenced more than once here, most notably when tersely critiqued by Ruffalo/Toschi.

A queasy sort of cinephilia emerges in all this as well: Bullitt and the vintage exploitation thriller The Most Dangerous Game (1932) get crucial mentions, Bay Area film buff Bob Vaughn (played by Charles Fleischer) figures eerily in the story for a time and Fincher has cast Brian Cox, the guy who first played Hannibal Lecter in the movies (Manhunter, 1986), as lawyer Melvin Belli. Plus the real-life Toschi is reportedly a background source for Bullitt, Dirty Harry and The Streets of San Francisco.

Cox’s Belli and Downey’s Paul Avery, a debauched banty rooster losing his way, are especially fine here. And Ruffalo and Gyllenhaal both do very solid work as relentless detectives, the one a pro and the other an amateur, whose lives come variously unraveled in the process.