Sir, please...

"Please, sir, you who knows everything, please do tell me, are there no limits? There is no frontier to be crossed? Who tells me where to stop? Please, answer!"

He answered in a loud and clear voice: "You will have to know where to stop! There are no guards, no line drawn on the floor. But yes, there is a limit. Yes, there is."

And then: "To make it easy on you I lend you a piece of... chalk!" And he disappeared. Laughing he was? I don't know. The fog...