I’ve been a security guard for eight years. Night shifts suit me. Fewer people, fewer conversations, you’re your own boss. Some people can’t understand how you walk empty buildings all night without losing your mind, but for me it’s the opposite. Silence is good. Empty is predictable.

I worked the building on Harrison Avenue for four of those eight years. Ten floors, roughly seventy tenants, a parking garage in the basement and a coffee shop on the first floor that closes at eight in the evening and leaves a smell of burnt milk in the corridor until morning. I know that building the way you know your own apartment in the dark. Every squeaking floor panel. Every elevator with its own personality. The third one from the left always opens with a three-second delay, like it’s thinking it over.

The sixth floor emptied out in March. The company that had been there ran layoffs and moved out. Not gradually. All at once, over one weekend. On Friday there were about forty people working up there. On Monday I came in for my shift, went up to check, and it was just empty. The furniture stayed: desks, chairs, a few filing cabinets, a coffee machine in the common area. Like the people had stepped out for a smoke break and never came back.

For the first few months I checked the sixth the same way I checked every floor. Open the stairwell door, shine the flashlight down the corridor, close it. It was dark up there, smelled like dust, and something in the ventilation system hummed. A low, steady sound I first thought was the air conditioning from the floor below, and then stopped thinking about at all.

I first saw light under the door of office 612 in early September. It was 2:47 in the morning.

I was walking the sixth-floor corridor with my flashlight, and at the far end, under the door marked 612, there was a narrow strip of yellow light. Not emergency lighting. The emergency lights here are green and run along ceiling fixtures. This was ordinary office light, warm and steady, like someone was sitting inside and working.

I stopped about fifty feet from the door. Stood there. Listened. Nothing but the ventilation.

I walked up, took the handle, and opened it. The office was empty. The overhead light was on, full brightness. Small office: desk at the window, two chairs on either side, a metal filing cabinet against the left wall. Blinds down. Nobody. I walked inside, opened the bathroom door attached to the office, shone my light in. Empty. Looked under the desk. Nobody. I switched the light off, logged it in my report, and continued down the corridor.

About five steps out I smelled coffee. Not stale coffee. Not the kind that soaks into the walls of a workspace over years. Fresh, hot coffee.

I stopped. Then I turned back, opened 612 again, turned the light back on. A white mug was sitting on the desk by the window. It had not been there when I looked a minute ago. I was certain of that because I had specifically walked the length of the desk. Now it was sitting right in the middle, near the edge closest to the window. I leaned in without touching it. Black coffee inside, no sugar, a thin column of steam rising off the surface. I touched the outside of the mug. Hot.

I took out my phone and photographed it. Logged it. Then I picked up the mug with a paper napkin from my pocket and carried it down to the security desk. Set it on the table and messaged the building manager. He called in the morning and said it was probably one of the cleaning crew wandering onto the wrong floor. They ran a check, went through all the contractors, checked the access card logs. Nobody had been on the sixth. No sign of unauthorized entry.

The next few nights were quiet. No light, the office dark like the rest. I started thinking it had been someone random, or that I had simply missed the mug on my first pass. That was an unpleasant thought, the idea that I might have missed something, but better than the alternative.

Nine days later, the light in 612 was on again. Exactly at 2:47.

I only noticed the time match because I had written it in my log both times. 2:47 the first night, 2:47 the second. I didn’t know what to do with that, so I just waited by the door. Leaned against the corridor wall and stood there for about five minutes, listening. No footsteps inside. No voices. Just the steady light under the door. I opened it. Empty office. Light on. Mug on the desk, same spot by the window.

I took it downstairs. Put it in the sink at the security desk, filled it with water, left it until morning. In the morning I stopped by 612 on my way out. The mug was on the desk. I stood in the doorway for a few seconds. Then I thought maybe I’d mixed it up, maybe I’d set it here instead of the sink. I picked it up. Checked the logo. Same insurance company, same lettering. I took it back down and locked it in my desk drawer this time. Photographed the drawer. Sent the building manager a second message. He didn’t reply.

The following night I opened the drawer at the start of my shift. Empty. I went up to the sixth. The mug was on the desk in 612.

After that I stopped touching it. For several weeks nothing new happened. The light in 612 came on every night at 2:47, I went in, saw the empty room and the mug, logged it, and left. The building manager stopped responding to my reports. The cleaning crew swore they never went to the sixth. I checked the access card logs myself every morning. Nobody was coming in. I got used to it. That was wrong of me, but I got used to it. It was one mug in an empty office. Strange but not frightening.

Then in mid-October I went into 612 and found the computer on.

The monitor had been sitting on the desk from the beginning, wide and flat and clearly outdated, the kind of thing people leave behind when they move out. The tower unit was under the desk. I had always known they were there. But they were not plugged in. I had checked that in the first few weeks, just to be sure there were no stray power sources up there. Now the screen was lit. Not in sleep mode. Fully active, bright.

I walked around the desk. A text editor was open on the screen. White background, cursor blinking at the end of the second line. I leaned down and read it. The document title was my full name. First and last, exactly as it appears in my employment records. The line beneath it said: “Don’t come back up here.” Nothing else. A blank document with one line.

I don’t know how long I stood over that screen. Long enough to make absolutely sure I wasn’t reading someone else’s name.

Then I walked out, closed the door, went back down to the desk, and sat. Two hours left in my shift. I sat through them without moving and without doing my rounds.

In the morning I submitted a transfer request to the day shift. I wrote that it was for personal reasons. That was a lie, but I didn’t know how to explain the truth without sounding like I was losing it. The transfer was approved a week later. In that week I didn’t go above the fifth floor. I didn’t call any elevators to the sixth. Once, late in the night, I heard a car go up and stay there. The indicator light on the panel at my desk showed six for several minutes straight. I watched it and didn’t press the call button.

In November a new tenant moved onto the sixth floor. A consulting firm. They used office 612 for storage, boxes and old equipment. Almost all the furniture was gone. The desk was cleared out. The computer too, as far as I know.

I’ve been on the day shift for six months now. Sometimes I stay a little late, help with the handoff, and leave the building after dark. I pass the elevator panel on the way out. I look at the indicator. Sometimes it shows the sixth floor.

I don’t go check.

I also recorded this story as a narration if you’d prefer to listen. Link in my profile