I've seen it now. And, worse, I can't mend a broken door, so they'll know it's got out, and they'll suspect the newest employee. Me.

It started a few days ago when i heard thudding, lop-sided footsteps on the ceiling of the top floor of the sportswear shop. I remarked to the fellow staff members who happened to be there, "Oh, didn't know there was a floor above this one!"

They immediately looked away from me and struck up a conversation about the weather between themselves.
I kept quiet that time, and did nothing.

The second time it happened was this morning. I was alone on the second floor, and lumbering footsteps again made themselves heard above me.

There was one door on the second floor I hadn't been through; the fire escape. I had been told that all the fire exits were automatically wired to an alarm, but i had also seen one of my colleagues open the fire escape in the basement which opened onto the city's labyrinthine underbelly, in order to dispose of some bags of packaging that were blocking the exit.

"It must just be a deterrent," I thought to myself, and opened the door. No alarm.
I found myself in a stairwell. The stairs going down were sure-looking concrete ones, designed to conduct people away from an emergency quickly and safely, but the stairs also led upwards. I began to climb, and as i ascended, dusty concrete gave way to creaking wood.

I came to a door, which had a rusted padlock below the handle, but was made of very old, woodworm-ridden pine.
"End of the line," I thought, "get back to work..."
Then I heard the noise. A rasping growl, very faint, followed by shuffling, thudding noises. About 10 feet, i thought, from where i was standing, on the other side of the door.
I still have no idea what possessed me, but my desire to see what was inside that room suspended all my reason, and I shoved hard against the door. The old wood splintered around the lock, releasing a burst of dust and spores, and the door opened, creaking violently.

For a few moments I could see nothing; my view was obscured by dust. As it cleared I began to make out the shape of a hulking contraption occupying most of the room. It looked like some kind of wire-drawing machine - an arrangement of wheels and pulleys with a kind of white residue all over them. The machine's workings were rusted and covered with oily black dust; it looked like it hadn't been working for some years. As my eye followed the mechanism, I suppressed a scream of horror as i found another pair of eyes staring right back at me.
They gazed balefully from a cage in the corner, and belonged to the most hideous thing I ever hope to see. It looked like a human being, but one of its legs was irregularly twisted and bloated, with things that looked like they could have been toes massing down one side of it. Its other leg was thin, hairless and wasted, and its hands bore thin, spidery digits; six on one, four on the other. In one of its armpits were two glands, like nipples, or earthworms' mouths, which dribbled a thin yellow fluid down the creature's side, forming a puddle on the sandy floor of the cage.
Its face was too horrific to begin to describe. I could look as far as yellow, decaying, drooping jowls before i had to avert my eyes.

The face spoke. Its voice was like the sound of sandpaper on dusty cloth, and as it breathed one word of explanation to me:
"Polyester."