The Fourth Mark

I went back to the studio before the building closed for the night.

I told myself the test would take five minutes. I would knock once, wait, and leave. I would not play the recording, and I would not improvise a second question because the first answer made me curious.

I brought a small audio recorder, a flashlight, and a strip of painter’s tape. The tape was for marking the dents, not for covering them. I had written that distinction in my notes before leaving home.

The hallway smelled faintly of floor cleaner. The adjoining studio was still empty. I checked it first, then checked it again from the doorway, as if the room might have filled while I looked away. Its bare walls held no shelves, mirrors, or furniture. A gray strip of conduit ran down one corner.

In my studio, I set the recorder on the floor opposite the marks and checked its levels. I kept the door open. The three dents were easy to find now that I knew where to look. Each sat at about the height of my knuckles.

I put a short strip of tape beside them and wrote the time on it. Then I stood in the spot where the camera had recorded my body facing the wall.

The first knock sounded dull. The second was louder. On the third, I kept my knuckle against the paint and waited.

Nothing came back.

I checked the recorder’s screen. Its level bar had moved with each tap and gone still. I had not expected a reply. I had expected to feel less foolish than I did.

The fourth knock was lighter than the others. I made it anyway.

A knock answered from inside the wall.

It was not loud. It was close enough that I felt the sound in my teeth before I identified its direction. My hand stayed raised. I counted four seconds, then lowered it.

The recorder kept running. No second sound came.

I leaned in to inspect the dents. The tape had shifted when my sleeve brushed it, so I pressed it flat and looked at the paint. Three marks. No change I could see. I turned the flashlight on and swept the beam across the surface, watching for a crack or a loose edge.

The light caught a pale dimple just below the others.

I stared at it for several seconds before touching it. The paint was unbroken. The indentation was shallow, almost too faint to feel with my fingertip. It was also separate from the three older marks, lower by the width of my hand and slightly to the right.

I took a picture. Then I checked the phone’s clock and the recorder. The knock and the dimple had come within the same minute. I could not tell whether the mark had been there when I arrived. I had inspected the wall, but not every inch of it. That mattered. I wrote it down anyway: possible fourth dent, noticed after fourth knock.