Zodiac was one of the stunning number of best of decade movies that came out in 2007- alongside There Will Be Blood, No Country for Old Men and a bunch of other movies that don't fit the point I want to make here- and I remember in reviews at the time, it was criticized somewhat for its formlessness. It has a number of seemingly key moments- a dramatic irony-laden announcement about Altamonte playing over one scene, the hero's wife leaving him, etc- but it never seems entirely to be about the loss of hope from the 60s to the 70s (the way Fear and Loathing in Las Vegas is) or about how pursuing even a noble goal obsessively can isolate you and break you apart from society (there are any number of things like this, but let's say 'Pretty much all of Batman'.) It's messy, and like No Country for Old Men, it doesn't really resolve in a satisfying way. How could it?
That said, I think the real key is the connection to Dirty Harry- one made explicitly within the movie, when the characters attend a (historical) showing. Dirty Harry was a fantasy in which the bad guys were really bad, the good guys were shackled by the rules and not by the nature of reality, and crime would continue getting worse and worse until it was finally and decisively punished. It was also, in a lightly fictionalized and highly stylized way, about the Zodiac killings. Zodiac shows those same events- and however much it adheres to reality, it's still fiction- but it shows them as part of a world where things don't work out cleanly, and in which people aren't pure and demonic evil but sort of messy, stupid bastards. The suspect it fingers for Zodiac is a pederast and a pretty gross man, but he's also pathetic and powerless, a loser janitor who seems hardly cogent enough to hate. His crimes end not because he's caught, but because of some other reason that the viewer never really knows. He might not even have committed some of the crimes he took credit for.
The structure of the movie is like There Will Be Blood in that it doesn't really seem to know where it's going a lot of the time, and it seems to show the viewer a lot of things that don't really relate. Yet somehow, by force of the scenes being placed in the relationship their given, they seem to work like a machine, and you as an audience member never think 'now why the hell am I looking at this.' When it ends, you feel like it's a fair ending, even though nothing is really finished, and everything anyone reached for just sort of drifted away.
I think that's a key element to a lot of modern fiction. We don't have depressing movies because we let the villains win, we have depressing movies because we don't know what a villain is or what it means to win or to lose. That kind of vaporous story has been around for a long time- it's what people look for in an Ozu movie, and a lot of indie sort of dramas- but introducing it even to genre fiction seems new to me, at least in the form it now takes. And all the other genre fiction seems like a lie, because it is one. Which is fine. But sometimes it's an ugly and hateful lie, like Dirty Harry, and Zodiac takes that lie away by making a world that contrasts it without being its opposite: it doesn't make you hate Dirty Harry by showing that real cops are disgusting pig assholes, because the cops in Zodiac are decent, hardworking, and intelligent guys. It makes you hate Dirty Harry by showing you all the things Dirty Harry tried to make you enraged about, and making them natural, reasonable, and in line with common sense. That's the best kind of criticism.
