“So,” Richie said flatly, “because Pat was a nice middle-class boy. A pillar of the community. That’s why he couldn’t be a killer.”

I didn’t want to have this argument, not in an airless observation room at some ungodly hour of the morning with sweat sticking my shirt to my back. I said, “Because he had things to love. He had a home—OK, it was in the arsehole of nowhere, but one look at it should have told you that Pat and Jenny loved every inch of the place. He had the woman he’d been loving ever since they were sixteen; still mad about each other, that’s what Brennan said. He had two kids who climbed all over him. That’s what holds the good guys together, Richie. They’ve got places to put their hearts into. They’ve got people to take care of. People to love. That’s what stops them from going over the edge, when a guy who wasn’t weighted down would be in free fall. And you’re trying to convince me that Pat just turned around one day and blew all that away, for no reason at all.”

“Not for no reason. You said yourself: he could’ve been about to lose the lot. The job was gone, the gaff was going; the wife and kids could’ve been about to go as well. It happens. All over this country, it’s been happening. The triers are the ones that snap, when trying doesn’t do any good.”

All of a sudden I was exhausted, two sleepless nights digging their claws in and dragging me down with all their weight. I said, “The one who snapped was Conor Brennan. Now there’s a man who’s got nothing left to lose: no work, no home, no family, not even his own mind. I’ll bet you any amount of money you want, when we start looking into his life we’re not going to find a close-knit circle of friends and loved ones. Nothing’s holding Brennan in place. He’s got nothing to love; nothing except the Spains. He’s spent the last year living like some kind of cross between a hermit and the Unabomber, all so he could stalk them. Even your own little theory hinges on the fact that Conor was a delusional freak show who was spying on them at three in the bloody morning. The guy’s not right, Richie. He’s not OK. There’s no way around that.”

Behind Richie, in the harsh white light of the interview room, Conor had put down the pen and was pressing his fingertips into his eyes, rubbing them in a grim, relentless rhythm. I wondered how long it had been since he had slept. “Remember what we talked about? The simplest solution? It’s sitting behind you. If you find evidence that Pat was a vicious sonofabitch who was beating the shit out of his family while he got ready to leave them for a Ukrainian lingerie model, then come back to me. Until then, I’m putting my money on the psycho stalker.”