"Then we scrutinised each individual square inch throughout the premises, including the two houses immediately adjoining, with the microscope, as before." (55)
Okay, we could—maybe—understand this kind of insane intrusion of privacy for a murder investigation, but we're just talking about a royal cover-up, here.
"What, for example, in this case of D—— has been done to vary the principle of action?" (98)
From Dupin's perspective, solving mysteries has nothing to do with re-establishing society's law and order and everything to do with following the law and order of, well, the universe.
"I am perfectly willing to take advice, and to pay for it. I would really give fifty thousand francs to any who would aid me in the matter." (86)
Sure, Dupin deserves a paycheck. In this case, though, G— is going to pay Dupin to help him cover up a deception, which he himself is being bribed to help cover up. Sounds like cash rules in this system.
"They are right in this much—that their own ingenuity is a faithful representative of that of the mass; but when the cunning of the individual felon is diverse in character from their own, the felon foils them of course." (98)
In other words, G—'s orderly methods are great for the average criminal, but D— isn't average. Another set of rules applies to him.
"For eighteen months the Minister has had her in his power. She has now him in hers." (120)
Assuming that G— gives the letter back to the queen, things have been returned to their original state. But is this really order—or is it simply another kind of chaos?