Sir Lyster rose and walked quickly over to the window. As he approached the tapping recommenced. Swinging back the curtain he disappeared into the embrasure.

The others heard the sound of the window being raised and then closed again. A moment later Malcolm Sage appeared, followed by Sir Lyster, who once more drew the curtain.

At the sight of Malcolm Sage, Mr. Llewellyn John's features relaxed from their drawn, tense expression. A look of relief flashed momentarily into Lord Beamdale's fish-like eyes.

"Thank G.o.d you've come, Sage!" cried Mr. Llewellyn John, with a sigh of relief as he grasped Malcolm Sage's hand as if it had been a lifebelt and he a drowning man. "I think you have met Lord Beamdale," he added.

Malcolm Sage bowed to the War Minister, then with great deliberation removed his overcoat, carefully folded it, and placed it upon a chair, laying his cap on top. He then selected a chair at the table that gave him a clear view of the faces of the three Ministers, and sat down.

"Why did you come to the window?" enquired Sir Lyster, as he resumed his own seat. "Did you know this was the library?"

"I saw a crack of light between the curtains," replied Malcolm Sage.

"It may be desirable that no one should know I have been here," he added.

"Something terrible has happened, Sage," broke in the Prime Minister, his voice shaking with excitement. He had with difficulty contained himself whilst Malcolm Sage was taking off his overcoat and explaining his reason for entering by the window. "It's--it's----"

His voice broke.

"Perhaps Sir Lyster will tell me, or Lord Beamdale," suggested Malcolm Sage, looking from one to the other.

Lord Beamdale shook his head.

"Just a bare outline, Sir Lyster," said Malcolm Sage, spreading out his fingers before him.

Slowly, deliberately, and with perfect self-possession, Sir Lyster explained what had happened.

"The Prime Minister and Lord Beamdale came down with me on Thursday night to spend the weekend," he said. "Incidentally we were to discuss a very important matter connected with this country's er-- foreign policy." The hesitation was only momentary. "Lord Beamdale brought with him a doc.u.ment of an extremely private nature. This I had sent to him earlier in the week for consideration and comment.

"If that doc.u.ment were to get to a certain Emba.s.sy in London no one can foretell the calamitous results. It might even result in another war, if not now certainly later. It was, I should explain, of a private and confidential nature, and consequently quite frankly expressed."

"And you must remember----" began Mr. Llewellyn John excitedly.

"One moment, sir," said Malcolm Sage quietly, without looking up from an absorbed contemplation of a bronze letter-weight fashioned in the form of a sphinx.

Mr. Llewellyn John sank back into his chair, and Sir Lyster resumed.

"Just over an hour and a half ago, that is to say soon after eleven o'clock, it was discovered that the doc.u.ment in question was missing, and in its place had been subst.i.tuted a number of sheets of blank paper."

"Unless it's found, Sage," cried Mr. Llewellyn John, jumping up from his chair in his excitement, "the consequences are too awful to contemplate."

For a few seconds he strode up and down the room, then returning to his chair, sank back into its comfortable depths.

"Where was the doc.u.ment kept?" enquired Malcolm Sage, his long, sensitive fingers stroking the back of the sphinx.

"In the safe," replied Sir Lyster, indicating with a nod a small safe let into the wall.

"You are in the habit of using it for valuable doc.u.ments?" queried Malcolm Sage.

"As a matter of fact very seldom. It is mostly empty," was the reply.

"Why?"

"I have a larger safe in my dressing-room, in which I keep my papers.

During the day I occasionally use this to save going up and down stairs."

"Where do you keep the key?"

"When there is anything in the safe I always carry it about with me."

"And at other times?"

"Sometimes in a drawer in my writing-table," said Sir Lyster; "but generally I have it on me."

"When was the doc.u.ment put into the safe?"

"At a quarter to eight to-night, just as the second dressing-gong was sounding."

"And you yourself put it in, locked the door, and have retained the key ever since?" Malcolm Sage had exhausted the interest of the sphinx and was now drawing diagrams with his forefinger upon the morocco surface of the table.

Sir Lyster nodded.

"I put the key in the pocket of my evening vest when I changed," he said. "After the other guests had retired, the Prime Minister raised a point that necessitated reference to the doc.u.ment itself. It was then I discovered the subst.i.tution."

"But for that circ.u.mstance the safe would not have been opened until when?" queried Malcolm Sage.

"Late to-night, when I should have transferred the packet to the safe in my dressing-room."

"Would you have examined the contents?"

"No. It is my rule to cut adrift from official matters from dinner-time on Sat.u.r.day until after breakfast on Monday. It was only in deference to the Prime Minister's particular wish that we referred to the doc.u.ment to-night."

"I take it that the rule you mention is known to your guests and servants?"

"Certainly."

"There is no doubt that it was the doc.u.ment itself that you put in the safe?"

"None; the Prime Minister and Lord Beamdale saw me do it."

"No doubt whatever," corroborated Mr. Llewellyn John, whilst Lord Beamdale wagged his head like a mandarin.

"Does anyone else know that it is missing?" asked Malcolm Sage after a short pause.

Sir Lyster shook his head.

"Only we three; and, of course, the thief," he added.

Malcolm Sage nodded. He had tired of the diagrams, and now sat stroking the back of his head.