Nobody is there...

You stand up and investigate but find that nobody is around. Strange... as you could have sworn that someone had knocked on the door. You are never wrong about these things as you have excellent hearing.

If this be some sort of trick to make you even more paranoid its working.... The thoughts of who could be messing with you continue that you don't notice a strange shadow is approaching from behind. Normally nothing can sneak up on you without your knowledge... unfortunately today is when you are far from your best.