This time, I moved books on shelves, cushions, ornaments, picture frames. I did it all quietly, as slowly and as carefully as I could, but then I opened the lid on a cigar box, now being used to store pencils, pens and paper, and the lid came away entirely in my hand, its mechanism totally broken. The whole thing clattered to the floor, the contents spilling out.

Shit.

Upstairs, I heard Healy shift.

I moved into the hallway and looked up the steps to the landing. He was at the top, a frown on his face, arms out in a What was that? gesture. I held up the empty cigar box and rolled my eyes, then returned to the living room, getting down on my hands and knees and scooping up the spilled pens, the pencils, paper, an eraser.

That was when I heard something.

It was a very gentle hum, a noise that faded into the background, but one I was certain I hadn’t heard when I’d first entered. It was coming from the floor. I pushed the cigar box aside and, still on all fours, hands pressed into the carpet, leaned down and looked under the sofa closest to me.

A light was blinking on its underside.

Getting to my feet again, I grabbed the bottom of the sofa and – as carefully as possible – tilted it back enough to see underneath. Screwed to the base was a small device, a digital readout on its front showing a series of red vertical bars. It was an audio equalizer, like the kind you’d find on an old stereo. A barely visible lead ran from the back of the device down and through a pinhole in the carpet.

That was why I hadn’t been able to find any wires.

They ran under the flooring.

Gently, I placed the sofa back and checked the rest of the room, then moved through to the kitchen. Another device, exactly the same as the one I’d found in the living room, was hidden inside the plastic casing of a strip light, its connection to the hard drive snaking off through another minuscule hole, this time in the ceiling. I had to take the entire light fixture apart in order to find both the device and the connecting wire, but they were there, the readout on the device bobbing up and down in response to my actions, even when they were minor. Afterwards, I stayed exactly where I was on a chair in the middle of the kitchen, silent, motionless, just observing it, and quickly realized that every sound registered, no matter how faint. We’d come into the house with no shoes in an attempt to conceal our search, but it had been a completely worthless act: even the softness of my breathing was getting a response, the equalizer pulsing into life.