Reflection of a Black Cat on the Stairs

There was a recent incident. I'm writing this, it's night outside and just remembering it makes me uneasy, because that room is behind the wall.
I was doing renovations in a room on the second floor. I live in a private house, and since I'm a broke-ass, I have to do it myself. Spackling, painting. The mess from it is fucking insane. For that reason I try to keep the door to the room closed and generally go into that part of the house less so I don't spread dust while renovating. I have three cats, they try to get into the closed-off part of the house and have their romps there, so they can then leave paw prints everywhere, so I don't let the cats into the room.
Under the stairs to the second floor there's a pull-up bar. I thought I'd work out like a pull-up guy, but fuck that, I'm lazy, at most I hang to relax my back and that's it. Opposite the stairs and the pull-up bar there's a window to the outside.
One time, after working in the room and pretty tired, I came down the stairs, and I feel my back hurting, like a fucking bitch. Okay, I'll hang on the pull-up bar for a bit. I hung. Opposite is the window. Outside the window it's night. In the black-as-space glass, like in a mirror, the room, the stairs, and the dick hanging on the bar are reflected. I was alone in the house that day. And then I see, on the stairs behind my back, a black cat is going up. Unhurried, carefully like that, jumping onto the steps and glancing at me. I didn't even turn around, I look at the reflection and think, well fuck, the bitch somehow slipped through, I need to go catch and escort the curious beast out. I jumped down, turned around, went up. No one. No cat. I checked the whole landing, the stairs, the room. No cat. WTF
Then I ran downstairs, and there the door to the other half of the house is shut tight. I went in there. In that half all the cats, including the black one, are fast asleep. I was slightly fucked up, even got the chills