If there were an Academy Award for choosing the best roles, my nomination would go to Jake Gyllenhaal.

Whether he's playing Homer Hickman in 1999's October Sky (one of my favorite films ever) or not-your-run-of-the-mill cowpoke Jack Twist in Brokeback Mountain (for which he was nominated for a real Oscar) or Marine sniper Anthony Swofford in Jarhead (possibly my favorite war movie ever), Gyllenhaal has a way of bringing depth of character to difficult parts.

And the good news is he's at it again.

In Zodiac, Gyllenhaal plays Robert Graysmith, the cryptogram-addicted San Francisco Chronicle cartoonist who takes it upon himself to solve the "Zodiac" killings that terrified the Bay Area beginning in the summer of '69 and continuing at least through the '70s.

It's a tale Graysmith knows well -- you might even say he wrote the book on it, because he did. Long after police had gone cold-case on Zodiac, Graysmith stuck to it, risking arrest himself for hounding anyone who might have the tiniest piece of information that could unlock the puzzle that becomes the focus -- or is it obsession? -- of his life.

Graysmith's book has now been taken to the screen by director David Fincher, who, after bouts with Fight Club, Panic Room and Se7en, has pretty well established his credentials as a maker of movies that are both tense and intense.

Fincher gets Zodiac off to a flying start with the lover's-lane killing of one Darlene Ferrin (Ciara Hughes), a married woman with a bad habit of forgetting her vows, and the near-fatal wounding of Mike Mageau (Lee Norris), her catch du jour, who's really just along for the ride.

As killings go, this would be fairly routine, if the alleged killer, the Zodiac, hadn't mailed a coded confession to the Chronicle -- and demanded its publication, or else.

It's at this point where Fincher and screenwriter James Vanderbilt make a very good decision: Instead of following Zodiac and turning his film into a West Coast Chainsaw Massacre, Fincher follows the guys who've set out to solve this case for one reason or another.

Yes, you've got some fairly nasty killings here, but most of the screen time goes to Graysmith, who's not supposed to be on this case, and Chronicle cop-beat reporter Paul Avery (Robert Downey Jr. as a hard-drinking junkie journalist. Hmmm. Can you say typecasting?).

Working both with them and against them are San Francisco detectives David Toschi (Mark Ruffalo) and William "Bill" Armstrong (Anthony Edwards), who spend much of the film wishing Graysmith and Avery would simply go away, even though it quickly becomes clear that neither pair can solve the case -- OK, we know it's the work of Zodiac; we just don't know who Zodiac is -- without the other.

The result is that Zodiac becomes less about the killings than about being creeped out by the killer -- or people we think might be the killer. Of these, the lead suspect is Arthur Leigh Allen (John Carroll Lynch). Whether the police are raiding his trailer or Graysmith is making unexpected eye contact with him, Allen has a way of making you wish you were somewhere else.

And the ante is jacked up considerably when Graysmith, a single dad, meets and marries Melanie (Chloe Sevigny), only to put in danger her life and the life of their children by insisting on pursuing the case to the very end. It's a nightmare that Fincher, Gyllenhaal and Sevigny bring to the screen in no uncertain terms.

Finally, kudos to whoever picked the songs for the soundtrack. From Donovan's "Hurdy Gurdy Man" to Boz Skaggs' "Lowdown," the Zodiac soundtrack helps make the '60s and '70s come alive. (I could have done without Gary Puckett's "Young Girl," but it fit.) Add to that the editing by Angus Hall (also of Panic Room fame), and you have the fastest-paced 2 1/2-hour film you'll ever cringe to.

Eventually, of course, the big question is: Who killed Ferrin and those who followed? Yes, that certainly is a big question.