“I suppose you know, Mr. Cuff,” he said, “that you are treading on delicate ground?”

“It isn’t the first time, by a good many hundreds, that I find myself treading on delicate ground,” answered the other, as immovable as ever.

“I am to understand that you forbid me to tell my aunt what has happened?”

“You are to understand, if you please, sir, that I throw up the case, if you tell Lady Verinder, or tell anybody, what has happened, until I give you leave.”

That settled it.  Mr. Franklin had no choice but to submit.  He turned away in anger—­and left us.

I had stood there listening to them, all in a tremble; not knowing whom to suspect, or what to think next.  In the midst of my confusion, two things, however, were plain to me.  First, that my young lady was, in some unaccountable manner, at the bottom of the sharp speeches that had passed between them.  Second, that they thoroughly understood each other, without having previously exchanged a word of explanation on either side.

“Mr. Betteredge,” says the Sergeant, “you have done a very foolish thing in my absence.  You have done a little detective business on your own account.  For the future, perhaps you will be so obliging as to do your detective business along with me.”

He took me by the arm, and walked me away with him along the road by which he had come.  I dare say I had deserved his reproof—­but I was not going to help him to set traps for Rosanna Spearman, for all that.  Thief or no thief, legal or not legal, I don’t care—­I pitied her.

“What do you want of me?” I asked, shaking him off, and stopping short.

“Only a little information about the country round here,” said the Sergeant.

I couldn’t well object to improve Sergeant Cuff in his geography.

“Is there any path, in that direction, leading to the sea-beach from this house?” asked the Sergeant.  He pointed, as he spoke, to the fir-plantation which led to the Shivering Sand.

“Yes,” I said, “there is a path.”

“Show it to me.”

Side by side, in the grey of the summer evening, Sergeant Cuff and I set forth for the Shivering Sand.

CHAPTER XV

The Sergeant remained silent, thinking his own thoughts, till we entered the plantation of firs which led to the quicksand.  There he roused himself, like a man whose mind was made up, and spoke to me again.

“Mr. Betteredge,” he said, “as you have honoured me by taking an oar in my boat, and as you may, I think, be of some assistance to me before the evening is out, I see no use in our mystifying one another any longer, and I propose to set you an example of plain speaking on my side.  You are determined to give me no information to the prejudice of Rosanna Spearman, because she has been a good girl to you, and because you pity her heartily.  Those humane considerations do you a world of credit, but they happen in this instance to be humane considerations clean thrown away.  Rosanna Spearman is not in the slightest danger of getting into trouble—­no, not if I fix her with being concerned in the disappearance of the Diamond, on evidence which is as plain as the nose on your face!”