"First," he began, "let us establish the obvious. The chance of there being a strange otherworldly being using graffiti to attack you in particular from another world is exceptionally unlikely. It is possible - very slimly possible - but highly improbable. The value of such a statement is almost zero. Correct?"
"Second, the symbol in question is based upon the description of a symbol from a book in connection with the works of Mr. Howard Phillips Lovecraft - this, its very design is intended to evoke a sense of otherworldliness. Thus, the chances of somebody placing it there to evoke such fears in some people are higher than the existence of the actual creatures.
"Now consider: the use of a symbol attributed to a god of madness - Hastur, if I am correct - being placed strategically around a city would give a sense of somebody being watched. Crude psychological architecture - but effective."
He noted my blank look and shook his head.
"Building ideas. Damaging thought patterns and rebuilding them in the image they desire. Gentrification of the psyche. So, we must examine the positioning and the people that pass the place regularly. Through this, we can gain a baseline of the intended victims, and see if you are among them. Then, we resolve the problem. But right now, I want to see this fog you mentioned - out by the docks, I believe. So get this car moving, or I can't promise what will happen in the next twenty-four hours."
"Because, Miss Quince, that feeling you had - that you were being watched?"
He gave a grim smile.
"That wasn't paranoia. We are being followed quite closely."