Things that go 'Bump' in the night.

Of all the things that go 'bump' in the night, the being called Slender Man is probably the scariest, and most dangerous, for two reasons. One, he usually doesn't go bump. He's usually silent. He's hard to notice. But you can see him. Once he starts following you, you're doomed. He will stalk you until you're his. And once you do notice him, you will start seeing him everywhere. You will be haunted by his presence, his unnatural aura. He will be outside your window in the darkness, staring in. His unearthly arms will reach for you, slipping through the smallest of cracks. There's no escape.
Reason two: who said anything about Slender Man going bump only in the night?
What's that behind you?