“I agree with Mr. Wilder, Dr. Huxtable, that you would have done wisely to consult me.  But since Mr. Holmes has already been taken into your confidence, it would indeed be absurd that we should not avail ourselves of his services.  Far from going to the inn, Mr. Holmes, I should be pleased if you would come and stay with me at Holdernesse Hall.”

“I thank your Grace.  For the purposes of my investigation, I think that it would be wiser for me to remain at the scene of the mystery.”

“Just as you like, Mr. Holmes.  Any information which Mr. Wilder or I can give you is, of course, at your disposal.”

“It will probably be necessary for me to see you at the Hall,” said Holmes.  “I would only ask you now, sir, whether you have formed any explanation in your own mind as to the mysterious disappearance of your son?”

“No sir I have not.”

“Excuse me if I allude to that which is painful to you, but I have no alternative.  Do you think that the Duchess had anything to do with the matter?”

The great minister showed perceptible hesitation.

“I do not think so,” he said, at last.

“The other most obvious explanation is that the child has been kidnapped for the purpose of levying ransom.  You have not had any demand of the sort?”

“No, sir.”

“One more question, your Grace.  I understand that you wrote to your son upon the day when this incident occurred.”

“No, I wrote upon the day before.”

“Exactly.  But he received it on that day?”

“Yes.”

“Was there anything in your letter which might have unbalanced him or induced him to take such a step?”

“No, sir, certainly not.”

“Did you post that letter yourself?”

The nobleman’s reply was interrupted by his secretary, who broke in with some heat.

“His Grace is not in the habit of posting letters himself,” said he.  “This letter was laid with others upon the study table, and I myself put them in the post-bag.”

“You are sure this one was among them?”

“Yes, I observed it.”

“How many letters did your Grace write that day?”

“Twenty or thirty.  I have a large correspondence.  But surely this is somewhat irrelevant?”

“Not entirely,” said Holmes.

“For my own part,” the Duke continued, “I have advised the police to turn their attention to the south of France.  I have already said that I do not believe that the Duchess would encourage so monstrous an action, but the lad had the most wrong-headed opinions, and it is possible that he may have fled to her, aided and abetted by this German.  I think, Dr. Huxtable, that we will now return to the Hall.”

I could see that there were other questions which Holmes would have wished to put, but the nobleman’s abrupt manner showed that the interview was at an end.  It was evident that to his intensely aristocratic nature this discussion of his intimate family affairs with a stranger was most abhorrent, and that he feared lest every fresh question would throw a fiercer light into the discreetly shadowed corners of his ducal history.