Richie said, “You told me yourself: ‘psycho’ isn’t a motive. All that about being upset because the Spains weren’t happy, that’s nothing. They’d been in trouble for months. You’re telling me the other night he just decided out of the blue, so fast he didn’t even have time to clean out his hide: There’s nothing on the telly, I know what I’ll do, I’ll head on down to the Spains’ and kill the lot of them? Come on, man. Here’s you saying Pat Spain didn’t have a motive. What the hell was this fella’s motive? Why the hell would he want any of them dead?”

One of the many ways that murder is the unique crime: it’s the only one that makes us ask why. Robbery, rape, fraud, drug dealing, all the filthy litany, they come with their filthy explanations built in; all you have to do is slot the perp into the perp-shaped hole. Murder needs an answer.

Some detectives don’t care. Officially, they’re right: if you can prove whodunit, nothing in the law says you need to prove why. I care. When I pulled what looked like a random drive-by, I spent weeks—after we had the shooter in custody, after we had enough evidence to sink him ten times over—having in-depth conversations with every monosyllabic cop-hating lowlife in his shit-hole neighborhood, until someone let slip that the victim’s uncle worked in a shop and had refused to sell the shooter’s twelve-year-old sister a packet of cigarettes. The day we stop asking why, the day we decide that it’s acceptable for the answer to a severed life to be Just because, is the day we step away from that line across the cave entrance and invite the wild to come howling in.

I said, “Trust me: I’m going to find out. We’ve got Brennan’s associates to talk to, we’ve got his flat to search, we’ve got the Spains’ computer—and Brennan’s, if he’s got one—to go through, we’ve got forensic evidence waiting to be analyzed … Somewhere in there, Detective, there’s a motive. Forgive me if I don’t have every piece of the puzzle in place within forty-eight hours of getting the bloody case, but I promise you, I will find them. Now let’s get this fucking statement and go home.”

I headed for the door, but Richie stayed put. He said, “Partners. That’s what you said this morning, remember? We’re partners.”

“Yes. We are. So?”

“So you don’t make the decisions for the both of us. We make them together. And I say we keep looking at Pat Spain.”

The stance—feet planted apart, shoulders squared—told me he wasn’t going to budge without a fight. We both knew that I could shove him back in his box and slam the lid on his head. One bad report from me and Richie was off the squad, back to Motor Vehicles or Vice for another few years, probably forever. All I had to do was touch on that, one delicate hint, and he would back off: finish Conor’s paperwork, leave Pat Spain to rest in peace. And that would be the end of that tentative thing that had begun in the hospital car park, less than twenty-four hours earlier.