Minister D-
the minister is almost an intellectual man match for dupin, but he is a villain instead of a hero.
He is also very daring.
He steals a letter from the royal lady while she is watching him.
He wants to gain political power, and as long as he has this letter, he can blackmail the lady into doing what he wants.
He understands very well how police work, and he hides the letter in one place they would never think of looking.