The room is dark. Of course it is, it's a dark room, a room where film is developed. If there was any light in here, it would ruin all the images.
Still, you are uneasy as you walk into the dark room. Perhaps it's just that it's not like natural darkness, but rather an artificial red darkness. It makes everything seem like it's splashed in blood. But you have to be in this room - it's part of your class, part of your assignment. You had to build a camera out of a box and you did. And now you have to develop the pictures you took.
You put your pictures into the tray of chemicals and you wait for them to develop. You try not to look at the walls, not to look at the shadows. There are so many.
For some reason, however, the only thing you can think of is a line from Discworld. You read those books to relax, but in this room, the line just comes to you: "Light thinks it travels faster than anything but it is wrong. No matter how fast light travels it finds the darkness has always got there first, and is waiting for it."
The picture is slowly developing. You can see it now. There are the trees and the buildings, but what's that? It looks like there's a dark smudge in the middle.
The smudge grows larger and larger and you realize it isn't a smudge at all. It's a shadow.
You hurry over to the lightswitch and you go to turn it on, when you realize that it's already on. The light has been on this entire time, but the room is still dark.
And as the dark envelopes you, you realize that it was always there, waiting for you.