“You are aware, Mr. Setter, that I am under the necessity of leaving London to-night, to attend the trial of Potts and Cameron to-morrow.”

“As a witness for the Crown.  I am, your grace.”

“I shall get back to London as soon as possible.  In the meantime, I wish you to pursue your investigations with the utmost diligence, sparing no expense.  Report in person every morning and evening to Lady Belgrade in this house, and by telegraph to me at Lone, in Scotland.  Use great discretion in wording your telegrams.  Avoid the use of names, or titles, or, in fact, any terms, in referring to the duchess, that may identify her.  I hope you understand me?”

“Perfectly, your grace.  I also understand how to speak and write in enigmas.  It is a part of my profession to do so,” answered Mr. Setter.

The duke then drew out his portmonaie, opened it, selected two notes of fifty pounds each and put them in the hands of Setter, saying: 

“Here are one hundred pounds.  Spare no expense in prosecuting this search.  Draw on me if you have occasion.”

The detective bowed.

At the same moment the footman re-entered the room, bringing a card on a silver waiter, which he handed to the duke.

The duke took it and read: 

“Your grace surely forgets that, as the husband of the heiress, you are the absolute master of the house, and your will is law here.  Do as you think proper.”

“You may go,” said the duke to the messenger, who immediately retired.

“Now, Mr. Setter, do you wish to search the premises, or examine the servants first?” inquired the duke.

“Examine the servants first, your grace; as I may thereby gain some clew to follow in my search.”

“Very well,” said the duke, again touching the bell.

The prompt footman re-appeared.

“Whom do you wish called first?” inquired the duke.

“The lady’s maid,” answered the detective.

“Go and tell the duchess’s maid that she is wanted here immediately,” said the duke.

The footman bowed and went away on his errand.

A few minutes passed, and the lady’s maid entered.

“This is—­I really forget your name, my good girl,” said the duke, apologetically.

“Margaret, sir; Margaret Watson,” said the lady’s maid, with a courtesy.

“Ay.  This is Margaret Watson, the confidential maid of her grace, Mr. Setter.  Margaret, my good girl, Mr. Setter wishes to put some questions to you, relating to the disappearance of your mistress.  I hope you will answer his inquiries as frankly and fearlessly as you have answered ours,” said the duke, as he took up a paper for a pretext and walked to the other end of the library, leaving the detective officer at liberty to pursue his investigations alone.

It is needless for us to go over the ground again.  It is sufficient to say that Detective Setter questioned and cross-questioned the girl with all the skill of an old and experienced hand, and at the end of half an hour’s sharp and close examination, he had obtained no new information.