Of all the overt symbols in the movie, the fire truck seriously scares us the most. This is the, um, creative roadblock that the Joker sets up at the start of that fantastic car chase. A heavily-armed police convoy is taking Harvey Dent to jail when they encounter an enormous fire truck sitting ablaze in the center of the road. Nolan accentuates the image with that spooky Hans Zimmer cello torture music, just so we don't miss the point.

Well what is the point exactly? For starters, while we've seen a lot of mayhem in movies, including a fair helping of cars on fire, few can match the sheer hypnotic power of the flames rising from that truck. It's unsettling and disturbing on an emotional level, not just a knee-jerk thrill, and as the scene progresses we know that the Joker has something truly awful in store. Even the dumb cops have figured it out: "We'll be like turkeys on Thanksgiving," one of them mutters as they detour down into the bowels of Gotham.

He's not speaking metaphorically.

So yeah, seriously spooky. And it affects us as much as the characters in the movie. But why? What's so different about this thing-on-fire that makes it so much more unsettling than all of the countless things-on-fire that came before it? The answer has to do with the fact that it's a fire engine: part of the big social safety net that everyone depends on. Whenever you run into trouble, whenever something bad happens, you know that you can dial 911, and help will come, often in the form of a fire truck just like the one burning merrily to the ground.

That truck yanks our safety net away. That truck says, "dial all the phone numbers you want, ain't nobody gonna come." And that truck does so with full knowledge that the Big Bad Wolf is waiting to gobble us up. It's the kind of thing that creates chaos: that turns fear into full-bore panic and make otherwise good people do terrible things to each other.

The Joker wants that of course; he's trying to turn Gotham into one big lunatic asylum. Terrifyingly enough, so were some real-life boogeymen that we were engaged in nebulous battle with. Osama bin Laden had not been caught when the film opened, which meant that the architect of 9/11 has escaped almost seven years of the greatest manhunt in history. His goals weren't all that different from the Joker's. He wanted to make Americans feel just as scared as those Gothamites in the movie, and he was betting that we would do terrible things if he could.

We're still discussing how and whether we did those terrible things or not (and we do not want to jump into that debate), but we sure knew how that terrible promise—"call for help, no one will come"—felt when we first heard it. And we knew that we wanted to rise above it, to get past it and show whoever made us scared that we weren't going to be bullied.

Kind of like a certain bat-eared guy who didn't let a spooky fire engine stop him.