Rival officers regularly attempt to engage me in behind-Manning’s-back rat-fuck convos on this subject. I shut them down. I don’t want to know Manning’s past. I accept his moods. I live with his irascibility. He’s Old Corps. Serving under a salt like Manning is the ideal way to be trained, even if you yourself don’t want to wind up as that kind of cop or that kind of person.

Manning’s standards are levels loftier than those of any other detective in DivSix. My job is by far the hardest of any junior detective. But every task Manning assigns me contains an element of instruction.

He’s teaching me.

He’s my mentor.

Manning instructs by means of mantras. His first is, “Never discount the obvious.” Manning believes that clues and evidentiary breakthroughs hide in plain sight. Look for what’s staring you in the face. The obvious things are the ones you miss.

Manning almost never talks to me, or to anyone else for that matter. The closest he comes to conversation is thinking out loud. My job is to listen. Entering the scene of the Davis murder nine days ago—a private dining room at the Century Association on 43rd between Fifth and Sixth—I hear him mutter to himself, “What would the dumbest sonofabitch in the world think in this situation?”

Manning’s second maxim is, “Never assume.”

Cadets at the academy are taught to be wary of assumption. Manning takes this two levels further. Flawed investigations, he says, are almost always “towers of speculation built upon foundations of assumptions.”

“When you enter a crime scene or begin an interrogation, you arrive with assumptions. You assume a suspect with needle tracks up and down his arm is a junkie or that the guy holding a smoking nine-millimeter is the killer. Stop thinking like that. Flush that shit out of your brain.”

An investigator’s responsibility before anything else, Manning believes, is to achieve and maintain awareness of his own unconscious assumptions—and to banish these from his thinking. “A little kid sees clearly because she is unburdened by assumptions. ‘The emperor has no clothes.’”

We’re approaching the new Baltimore Harbor Tunnel. The largest and most desperate homeless encampment on the East Coast squats here, almost three hundred thousand souls displaced by the rising water and funneled into camps above the rebuilt seawall. The train slows nearing the tunnel entrance, not so much for attacks, as the police and army have routed most of that, but for suicides, even mass suicides, of people hurling themselves in the dark onto the tracks.

Our businessmen seatmates come alert as the train decelerates. But we’re good today. Other than a broadside of obscene signs and graffiti, we pass through without incident.