“And he wiped his own prints off the barrel and cartridges?”

“I hear you,” I say. “I think you’re on to something, Castro, but you have to admit it’s thin.”

“Circumstantial, I know. But here’s another piece of circumstantial evidence. The trajectory of the bullet? If Detective Thomson really shot himself, he held the gun at a strange angle – ”

“That’s what Dr. Bridger said.”

“Look at this.”

He produces a plastic-bound report just like the one he gave me on the Morales shooting, flipping to another one of his 3-D reconstructions. This one has two panels. In the first, a crash-test dummy representing Thomson holds a pistol to his head, canting the gun at a forty-five degree angle. A red line from the barrel penetrates his head, continuing up through the roof of the vehicle.

“That’s not right, is it?” he says. “The bullet didn’t go out the roof. It was in the door pillar. But if he was sitting upright, the trajectory would have sent it through the ceiling. So he was leaning toward the door, like this.” He points to the second panel, where the dummy rests his head against the pillar. Now the red line is flat, running side to side, and the head is at an angle. “But why would he do that? It’s a strange way to shoot yourself, isn’t it?”

Yes, it is. But it makes perfect sense if someone else was in the car. The shooter drew on Thomson, punching the pistol forward into the side of his head. It struck him, pushing his skull against the door pillar, and then the shooter fired.

“You mind?” I ask, snatching the empty pistol.

Not only does Castro not mind my putting the gun to his head, he’s eager to arrange things just so. We set our chairs side by side against the wall, then he sits down and drapes his hands over an imaginary steering wheel. I get beside him, my finger away from the trigger, and slow-motion Thomson’s pistol through the air, from my lap to a point just above his ear. As soon as it touches, he slides toward the wall. When his head taps sheetrock, the angle of the gun is pretty much straight.

“It works.” I put the weapon down. I let out a sigh. “So that’s what happened.”

The sudden grin on Castro’s face, like I’ve just awarded him an A+ on his class project, reminds me again how green the kid is. Green or not, though, he’s sharp. And if there were a mirror in the room, it wouldn’t surprise me to see an equally stupid-looking grin on my own face, because my excitement has to be on par with his, if not higher.

“Good work, Castro. Really. Now, I’m going to have to ask you to do me a favor, and it won’t be easy for you. This information? We need to keep it between the two of us right now.”

His smile fades. “But why?”

“Think about it. If your theory is right, this wasn’t a premeditated thing. Something happened and the killer decided there was no other choice. He pulled his gun and fired.”

“And?”

“And it just so happened his gun matched Thomson’s. So does mine, Castro. So does yours. You see what I’m saying?”

“Anybody could have a sig Sauer.”

“Sure they could,” I say. “But we both know that’s not the deal here, right? For the time being, I need this to look like a suicide investigation, and if you shoot your mouth off about this theory, the wrong people are going to find out I’m on to them. So for now, can we keep it between the two of us?”

“I already told the other guys,” he says quietly.

“But they didn’t listen, did they? Let’s leave it at that.”

The struggle on his face lasts a second or two, then he nods with resignation. Playing along means no immediate recognition for his work, but since his colleagues aren’t backing him, there’s not much risk of professional trouble. This way, at least, he can feel like he’s in the know, keeping secrets for the detective in charge.

“Okay,” he says, sticking a hand out. “Deal.”

There’s no way he’ll let me go without a handshake, so I give in. His palms are damp and warm. I wait until I’m safely hidden behind the elevator door to wipe mine dry.

Get a cop to open up about his personal frustrations, and once you get past the office politics, the slow advancement, and the various fractures in the justice system, he might, assuming he’s the philosophical type, start talking about the gap between knowledge and proof. I’ve been cut by both sides of the blade, knowing things I couldn’t prove and proving things I didn’t really believe. The idea that there’s any connection between what we believe and what we can prove goes out the door early, at least it does if you’re paying attention.

I’ve sent men to prison with no idea whether they did the crime or not. The case was there, so I made it. The ultimate decision belongs to the judge or jury, something I took comfort in once, though not so much anymore. If we had to know – really know – what happened, no one would ever go to jail. Fortunately, you can prove things in court that you can never truly know.

By the same token, you can know things that can’t ever be proven. And that knowledge often has a certainty to it that the evidential sort never does. There are these unproven things about which I have a quasi-religious certainty, things I would act on more readily than anything I could support with mere evidence. I can’t explain this exactly, but anyone who has trodden long enough on the line between fact and truth will tell you the same.

Or not. I can only speak for myself.

When I try imagining Keller’s hand on the murder weapon – or Salazar’s, which is easier somehow – the mental image is absurd, almost laughable. Even so, it’s my new article of faith. Castro’s hunches fit in with Bridger’s qualm, but it can all be explained away. Everything can. Only I know what these men are capable of. I bear the marks on my flesh.

It’s not enough. It won’t convince Hedges or Bascombe. It won’t satisfy Wilcox. And if I go to any of them, I’ll tip my hand. That’s why Castro has to keep quiet. That’s why I have to tread very carefully, planning my next moves for maximum effect.

Back at my desk, I put in another call to Cavallo. She hasn’t returned yesterday’s call, and I’m beginning to think she never will. She’s probably relieved to see the back of me. Vance, the man who’s supposedly holding a box from Thomson, hasn’t called me, either. That’s the lead I want to follow up, and it’s as simple as feeding his phone number into the computer.

While I’m copying down the contact info on Mr. Vance Balinski, a Caucasian male aged thirty-four years, residing in an Uptown condo with a ten-year-old Mercedes coupe registered to his name, Detective Aguilar appears at my elbow, black eyes sparkling in his lobster-red face, a photo lineup clutched in his hands. Thanks to his gang experience, he caught my shooting, and now he perches on my desk and hums a little fanfare.

“What’re you so chipper about?”

He hands over the lineup, along with a well-chewed ballpoint pen. “You know the drill.”

Right away, I recognize the shooter. Looking at his mug shot, I’m surprised my guard wasn’t up from the get-go. A tough customer with the faraway stare of a man who’d gut you just to see whether his knife was sharp.

Aguilar nudges my chair with his foot. “You see him here or not?”

I circle the right man and hand the page back.

He nods in satisfaction, humming another bar. “Dude’s name is Rafael Ortiz, an enforcer for LTC. Which means the cholos in the house with Morales were his boys.” He gives me one of his unreadable stares. “Any reason they’d want to clip you?”

“Something to do with the case, I assume. Beats me what it is.”

We commune silently, aware that I’ve only stated the obvious. Then he starts humming again, like a man whose case is down. He folds the sheet and tucks it into his jacket. “You won’t have to worry about this Ortiz, anyway.”

“Why?” I ask. “You haven’t picked him up already, have you?”