French photographer David One `s "Presence" photo essay takes that feeling of when you think someone is watching / following you  but you can't and puts it into a visual form.  Perhaps that description was a tad vague but the pictures he created are nothing less then spectacularly moving and emotional. You find yourself feeling the loss and heartbreak the "ghost" as well as the person mourning. Where there is sadness and death there is also beauty. Take a look for yourself.