"A mark?"
"Yes; an invisible mark, which I can render visible with the aid of a chemical process."
"Well, well!" said Cauvignac, "that is certainly a most ingenious device, monseigneur; but you must be careful that he doesn't suspect the trap."
"Oh! there's no danger of that; who do you think is likely to tell him of it?"
"True! true!" replied Cauvignac; "not Nanon, surely, nor I—"
"Nor I," said the duke.
"Nor you. So you are right, monseigneur; you cannot fail to know some day who the man is, and then—"
"Then, as I shall have kept my agreement with him, for he will have obtained whatever he chose to use the signature for, I will have him hanged."
"Amen!" said Cauvignac.
"And now," continued the duke, "as you can give me no information concerning the miscreant—"