Number 16 was in even worse shape than I’d thought. There were big gouges all the way down the front steps where the builders had dragged the fireplaces away, and someone had nicked the wrought-iron railings on either side, or maybe the Property King had sold them too. The whacking great sign announcing “PJ Lavery Builders” had fallen down the well by the basement windows; nobody had bothered to retrieve it.

Kevin asked, “What are we doing?”

“We’re not sure yet,” I said, which was true enough. All I knew was that we were following Rosie, feeling our way step by step and seeing where she led us. “We’ll find out as we go, yeah?”

Kevin poked the door open and leaned forward, gingerly, to peer in. “If we don’t end up in hospital first.”

The hallway was a tangle of crisscrossing shadows, layered half a dozen deep where faint light seeped in from every angle: from the empty rooms with their doors pulled half off, through the filthy glass of the landing window, down the high stairwell along with the cold breeze. I found my torch. I may be out of the field, officially, but I still like being ready for the unexpected. I picked my leather jacket because it’s comfortable enough that it almost never comes off, and it has enough pockets to hold all the basics: Fingerprint Fifi, three small plastic evidence bags, notebook and pen, Swiss Army knife, cuffs, gloves, and a slim, high-powered Maglite. My Colt Detective Special goes in a specially made harness that keeps it snug at the small of my back, under my jeans waistband and out of sight.

“I’m not joking,” Kevin said, squinting up the dark stairs. “I don’t like this. One sneeze and the whole place’ll come down on top of us.”

“The squad has a GPS tracker implanted in my neck. They’ll come dig us out.”

“Seriously?”

“No. Man up, Kev. We’ll be fine.” And I switched my torch on and stepped into Number 16. I felt the decades’ worth of dust specks hanging suspended in the air, felt them shift and stir, rising up to whirl in cold little eddies around us.

The stairs creaked and flexed ominously under our weight, but they held. I started with the top front room, where I had found Rosie’s note and where, according to Ma and Da, the Polish boys had found her suitcase. There was a great jagged hole where they had ripped out the fireplace; the wall around it was crowded with faded graffiti explaining who loved who, who was gay and who should fuck off. Somewhere on that fireplace, on their way to someone’s Ballsbridge mansion, were my initials and Rosie’s.