I told him of the experiment with the opium, and of what had occurred afterwards at the bank in Lombard Street.  He was greatly struck by the experiment—­it was something entirely new in his experience.  And he was particularly interested in the theory of Ezra Jennings, relating to what I had done with the Diamond, after I had left Rachel’s sitting-room, on the birthday night.

“I don’t hold with Mr. Jennings that you hid the Moonstone,” said Sergeant Cuff.  “But I agree with him, that you must certainly have taken it back to your own room.”

“Well?” I asked.  “And what happened then?”

“Have you no suspicion yourself of what happened, sir?”

“None whatever.”

“Has Mr. Bruff no suspicion?”

“No more than I have.”

Sergeant Cuff rose, and went to my writing-table.  He came back with a sealed envelope.  It was marked “Private;” it was addressed to me; and it had the Sergeant’s signature in the corner.

“I suspected the wrong person, last year,” he said:  “and I may be suspecting the wrong person now.  Wait to open the envelope, Mr. Blake, till you have got at the truth.  And then compare the name of the guilty person, with the name that I have written in that sealed letter.”

I put the letter into my pocket—­and then asked for the Sergeant’s opinion of the measures which we had taken at the bank.

“Very well intended, sir,” he answered, “and quite the right thing to do.  But there was another person who ought to have been looked after besides Mr. Luker.”

“The person named in the letter you have just given to me?”

“Yes, Mr. Blake, the person named in the letter.  It can’t be helped now.  I shall have something to propose to you and Mr. Bruff, sir, when the time comes.  Let’s wait, first, and see if the boy has anything to tell us that is worth hearing.”

It was close on ten o’clock, and the boy had not made his appearance.  Sergeant Cuff talked of other matters.  He asked after his old friend Betteredge, and his old enemy the gardener.  In a minute more, he would no doubt have got from this, to the subject of his favourite roses, if my servant had not interrupted us by announcing that the boy was below.

On being brought into the room, Gooseberry stopped at the threshold of the door, and looked distrustfully at the stranger who was in my company.  I told the boy to come to me.

“You may speak before this gentleman,” I said.  “He is here to assist me; and he knows all that has happened.  Sergeant Cuff,” I added, “this is the boy from Mr. Bruff’s office.”

In our modern system of civilisation, celebrity (no matter of what kind) is the lever that will move anything.  The fame of the great Cuff had even reached the ears of the small Gooseberry.  The boy’s ill-fixed eyes rolled, when I mentioned the illustrious name, till I thought they really must have dropped on the carpet.