His face was expressive enough in its frowning contempt, but he said nothing for a moment, during which his eyes met mine mercilessly.

“So you find the work too hard, eh?” he asked.

“The work is just what I should have chosen, your Grace,” I answered.  “I like hard work, and I expected it.  The trouble is that I have succeeded no better than Lord Ronald.”

My words were evidently a shock to him.  He half opened his lips, but closed them again.  I saw the hand which he raised to his forehead shake.

“What do you mean, Ducaine?  Speak out, man.”

“The safe in the study has been opened during the night,” I said.  “Our map of the secret fortifications on the Surrey downs and plans for a camp at Guilford have been examined.”

“How do you know this?”

“I tied the red tape round them in a peculiar way.  It has been undone and retied.  The papers have been put back in a different order.”

The Duke was without doubt agitated.  He rose from his chair and paced the room restlessly.

“You are sure of what you say, Ducaine?” he demanded, turning, and facing me suddenly.

“Absolutely sure, your Grace,” I answered.

He turned away from me.

“In my own house, under my own roof,” I heard him mutter.  “Good God!”

I had scarcely believed him capable of so much feeling.  When he resumed his seat and former attitude I could see that his face was almost gray.

“This is terrible news,” he said.  “I am not at all sure, though, Mr. Ducaine, that any blame can attach itself to you.”

“Your Grace,” I answered, “there were three men only who knew the secret of that combination.  One is yourself, another Colonel Ray, the third myself.  I set the lock last night.  I opened it this morning.  I ask you, in the name of common sense, upon whom the blame is likely to fall?  If I remain this will happen again.  I cannot escape suspicion.  It is not reasonable.”

“The word was a common one,” the Duke said half to himself.  “Some one may have guessed it.”

“Your Grace,” I said, “is it likely that any one would admit the possibility of such a thing?”

“It may have been overheard.”

“It has never been spoken,” I reminded him.  “It was written down, glanced at by all of us, and destroyed.”

The Duke nodded.

“You are right,” he admitted.  “The inference is positive enough.  The safe has been opened between the hours of ten at night and seven o’clock this morning by—­”

“By either myself, Colonel Ray, or your Grace,” I said.

“I am not sure that I am prepared to admit that,” the Duke objected quietly.

“It is inevitable!” I declared.

“Only the very young use that word,” the Duke said drily.

“I spoke only of what others must say,” I answered.

“It is a cul de sac, I admit,” the Duke said.  “Nevertheless, Mr. Ducaine, I am not prepared without consideration to accept your resignation.  I cannot see that our position would be improved in any way, and in my own mind I may add that I hold you absolved from suspicion.”