Private Eye with a Heart of Gold
What's the best way to get to know a private eye? By watching him solve a mystery, of course. (If you were going to say, "Go through his underwear drawer," you take second place.)
That's how we get to know Jake. Chinatown doesn't scream "This is a good guy!" by showing him save a wounded kitten. It gets at Jake's essential goodness by showing him working. As we see him continuing to pursue this mystery relentlessly, we start to realize: Jake isn't just a typical, sleazy Hollywood private eye.
He has a deep need to solve this mystery and a sincere desire to help Evelyn Mulwray. Although at one point he insists that he's trying to solve it just because he's mad that his nose gets cut by a bad guy, we know that can't be the case.
Initially, we see that he makes a living by exposing extramarital affairs. Obviously, some people might consider this a kind of sleazy or dubious way to get by, and Jake is pretty sensitive about the matter. At one point, when a customer in a barbershop criticizes him, Jake explains:
GITTES: Look, pal—I make an honest living. People don't come to me unless they're miserable and I help 'em out of a bad situation. I don't kick them out of their homes like you jerks who work in the bank.
And when Evelyn Mulwray (who actually turns out to be a woman named Ida Sessions impersonating the real Evelyn) first comes to him, he tells her that if she loves her husband, she should leave. Of course, she stays and lures Jake into the trap that will help doom Hollis Mulwray.
So, Jake is a private eye, with a lot of the private eye's seemingly questionable qualities—he tells unfunny racist jokes, he smirks, and he looks really at home in dimly lit offices.
But the thing is, he doesn't love or relish the dirty side of his job. As Roger Ebert points out:
He can be raw, he can tell dirty jokes, he can accuse people of base motives, but all the time there's a certain detached under-level that makes his character sympathetic: like all private eyes, he mud wrestles with pigs, but unlike most of them, he doesn't like it. (Source)
Ebert—as per usual—nails it. (Although, we have to say that "mud wrestling with pigs" sounds kind of cute and fun.)
Don't Mess with the Nose
As the mystery deepens, Jake discovers that someone's stealing water from L.A. (le gasp!) and that Hollis Mulwray has been murdered (le double gasp!). He also realizes that the Evelyn Mulwray who contacted him was actually an impostor using him to set-up Hollis Mulwray.
The real Evelyn threatens to sue him, but then she backs off with surprising ease. Adding injury to insult, a knife-wielding bad guy slices Jake's nostril open when he goes to investigate the site of Hollis's drowning at a reservoir.
Angry, Jake tells Evelyn:
GITTES: Okay, go home, but in case you're interested, your husband was murdered. Somebody's been dumping thousands of tons of water from the city's reservoirs and we're supposed to be in the middle of a drought. He found out about it and he was killed. There's a waterlogged drunk in the morgue, involuntary manslaughter if anybody wants to take the trouble—which they don't. It seems like half the city is trying to cover it all up, which is fine by me. But Mrs. Mulwray, I goddamned near lost my nose. And I like it. I like breathing through it. And I still think that you're hiding something.
And we think that Jake's hiding something behind his "I heart my shnoz" speech. Sure, he likes his nose. But it's not just air that Jake's sniffing at this point in the movie. He smells a scandal, and he's too much of a stand-up guy to sit back and let the mystery of a murder, a woman pretending to be another woman, and a dehydrated metropolis go unsolved.
Not on his watch.
Here's some proof: Jake was sneaking around the reservoir, trying to unravel the mystery, before the knife incident even happened. He wants to know the truth and to help the county retain its stolen water (although he's unwilling to get sappy and sentimental about this stuff when he talks about it).
And he also does want to help Evelyn, though he also suspects her of knowing more than she's willing to say about her husband's murder.
But despite wanting to know the truth, he finds that, as Jack Nicholson screamed at Tom Cruise in A Few Good Men, he "can't handle the truth!" At one point Evelyn gives him a strong hint:
EVELYN: I want you to listen to me—my father is a very dangerous man. You don't know how dangerous. You don't know how crazy.
But, despite his general aptitude as a detective, Jake still gets stuck on the idea that Evelyn accidentally killed Hollis during an argument and pushed him into the saltwater pond where he might've hit his head on a rock. He can't break out of his more traditional ideas about what must be going on—can't sense the depths of the madness in Noah.
"As Little as Possible…"
To understand why Jake cares, we need to look into his past working as a detective in Chinatown. After finally sleeping with Evelyn, he tells her in bed that he tried to do "as little as possible" in Chinatown. (What? Not even rustle up game of Mahjong? Branch out a little, Gittes.)
This is because, faced with a foreign culture, he and the other detectives were completely unsure about what they were doing…and how they were being manipulated. Not only were they so unaware of Chinese culture that they probably wondered why lo mein didn't come with marinara and meatballs, but they also were like toddlers in an Olympic pool—out of their depth.
Jake alludes to this:
GITTES: I thought I was keeping someone from being hurt and actually I ended up making sure she was hurt.
What was this earlier incident? Was Jake romantically involved with this girl, like he now is with Evelyn? We never find out, though there's a dark hint that the same tragedy is repeating itself over again—except in this case, Evelyn will the be the woman who Jake tries to help but who ends up getting hurt.
If this was Who Framed Roger Rabbit? (which is partially based on Chinatown) Roger Rabbit would probably shout, "Here we go again!" at this point.
This helps us understand why Jake became a private eye, too. He decided to do less complicated work, simply identifying cheating partners, instead of getting entangled in deceptions. Ironically, his attempt to flee these complexities ends up leading him into a new net of duplicity, when Noah Cross uses him to inadvertently frame Hollis Mulwray for adultery and set the stage for Hollis's "suicide" (actually a murder).
Jake can't get away from Chinatown—and the movie's final scene drags him back to the same place and the same state of confusion, sadness, and frustration that he faced there before.
After Evelyn is shot by the police in Chinatown, and her father Noah Cross takes the granddaughter—who he conceived through incest with Evelyn—Jake looks on in stunned horror. Before he gets pulled away by his assistant, he murmurs to himself, "…As little as possible."
All of his efforts to solve the mystery and all his brilliant detective work couldn't prevent Evelyn from getting hurt…and he realizes that he and Evelyn both would've been better off if he had never touched the case.
We'd say "womp womp," but "womp womp" seems a little weak when a) a triple murder and b) an incestuous psychopath bent on parching the City of Angels are in the mix.