From the introduction:
You may see him out of the corner of your eye, or in a reflection, or caught on tape... a man, eight feet tall and impossibly thin in a simple, plain black suit, with a blank, featureless face.
But if you should see him, even accidentally, then you've caught his attention. Even if you're just a student filmmaker, who spots someone (something?) on the tape, which you didn't see while you were filming... a sight you couldn't have missed, but did anyway.
He doesn't seem threatening... odd, creepy, but distant. And yet, the stories you hear... a bizarre, implacable outsider and people who go mad or disappear or worse... and the more you learn, the stranger things get... you've caught the eye of the Slenderman.