In the endless, nighttime metropolis of Downtown, there are some buildings which are not home to bars or nightclubs - offices, high-rises, other places that sleep through the night. Sometimes a window is lit in one, and a dark figure stands silhouetted, and you can tell that they are looking at you - and that thought fills you with inexplicable dread.
But when you try to actually make out the figure, the light goes out, and the sense of being seen disappears.