I had a job maintaining a labyrinthean complex of corridors. They looked like something out of an office or hotel, slightly dated with faded blue carpet and thick, pale wood fire doors. The corridors had other doors in them, but they only ever led to more corridors. There were windows here and there, only ever on one side, that only let in a hazy golden light. You couldn't see through them.
My job involved updating the labels on the doors that detailed what could be found on that corridor, such as files, books, plants, and so on. I had updated a few doors up till now and was heading to another corridor; the one I was in was kind of dark. Going through the door, I found myself in a hazily lit corridor stretching off the the left. Back to the door, the writing in pencil was getting faint so I started to write "Files" with my marker, only it had just run out of ink. I went back through to find a marker pen I saw in a basket.
Just then I started hearing something like a piano key being periodically struck. It was fairly detuned and slightly bit-crushed, somewhere around C4 on the keyboard. It was getting louder and louder. As I headed back to the door, it opened, and another employee was standing there. He looked right at me with this nervous expression before looking past me down the corridor. I turned to see what he was looking at, and sure enough there was a figure of a small girl shrouded in shadow standing about 40 metres away, everything past her was dimmer.
I suddenly this had happened before, after which I had been given a briefing with some others about this phenomenon. If you're in a corridor and you start hearing that sound, you're to leave it immediately because it means she is close. How did I forget this? I went back through the door with the other guy and the door almost closed behind us. I'm trying to reach out to pull the door shut but my body doesn't move. Then I woke up.