"That seems perfectly clear," Hatch remarked smilingly. "That is, the nature of the problem itself is clear, but the solution is as far away as ever."
The Thinking Machine arose abruptly and passed into the adjoining room. After a while Hatch heard the telephone bell. It was half an hour or so before The Thinking Machine returned.
"The person who owns the knife will call to see me this afternoon at 3 o'clock," he announced.
Hatch half rose in his astonishment, then sank down again.
"Whoever it is will be arrested the moment the police learn of it," he said after a pause.
"On what charge?"
"Murder. It's a plain circumstantial case."
"If he is arrested," said the scientist, "there will be some international complications."
"Who is he?" asked Hatch.
"His name will appear in due time. Meanwhile find out for me if there has ever been a report to the police of any robbery, in which a dagger is mentioned in any way."
Wonderingly, Hatch went away to obey instructions. He found no trace of any such robbery for half a dozen years back. There were several entries on the police books, and of these he made a record.
At 1 o'clock that afternoon he was again in Cambridge working with the police and half a dozen reporters in an effort to get some light on the question of the girl's identity. Later he went to the real estate office of Henry Holmes & Co. seeking further light there. It was not forthcoming.
"Did this man, Wilkes, sign anything?" he asked; "a lease, or anything of that sort? A sample of his handwriting might be useful now."
"No," was the reply. "We did not consider a lease necessary."
Meanwhile the police had apparently exhausted every means of finding out who and what Charles Wilkes was. It was clear from the beginning, to them at least, that the name Wilkes was a fictitious one. There was no reason to suppose that if Wilkes rented the house with the deliberate intention of murder that he would give his real name. By the wildest stretch of the imagination they could find no motive for the murder. It was not any of the ordinary things. Yet it was deliberate. They regarded the golden dagger as the key to the entire mystery. There they stopped.
At 3 o'clock Hatch returned to the home of The Thinking Machine. He had hardly been ushered into the little reception room when the doorbell rang and the scientist in person appeared. Accompanying him was a stranger; dark, swarthy and with the coal black beard of the Orient.
Hatch was introduced to him as Ali Hassan. Then The Thinking Machine produced the photograph of the dagger.
"Is this the correct picture?" he asked.
The stranger examined it closely.
"It seems to be," he said at last.
"Is there another dagger like that in existence?"
"No."
"How did it come into your possession?"
"It was a gift to me from the Sultan of Turkey," was the reply.
III.
Gravely Mr. Hassan sat down while The Thinking Machine resumed his seat in the big chair opposite. Hatch was leaning forward eagerly to catch every word. The story of the man who owned the wonderful golden dagger was one which the great public would naturally want to know.
"Now," began The Thinking Machine, "would you mind telling us a little of the history of the dagger?"
"It is not a story to be told to infidels," was the reply. "I mean, of course, unbelievers. I will answer any question that you see fit to ask if I can do so."
A little expression of perplexity crept into the squinting eyes of The Thinking Machine; then it passed as suddenly as it came.
"You are a Mohammedan?" he asked.
"Yes."
"Is there any religious significance attached to the dagger?"
"Yes, it is sacred. A gift from the Sultan-my imperial master-and blessed by the royal hand is always sacred to a subject. It may not be even seen by the eyes of an unbeliever."
Hatch straightened up a little, and The Thinking Machine readjusted himself in the big chair.
"You were educated at Oxford?" he asked irrelevantly.
"Yes. I left there in 1887."
"You did not embrace the Christian religion?"
"No. I am a Mohammedan, loyal to my master."
"Would you mind saying for what service the Sultan so honored you?"
"I cannot say that. It was a service to the crown at a time when I was secretary of the Turkish Embassy in England."
"Under what circumstances did this dagger leave your possession?" asked The Thinking Machine quietly.
"It has not left my possession," was the equally quiet reply. "It would be sacrilege if it did. Therefore I still have it-closely guarded."
Frankly, Hutchinson Hatch was amazed. His manner showed it clearly. The Thinking Machine was still leaning back in the chair staring upward.
"I understand then," he said after a little pause, "that the dagger, of which this is a photograph, is in your possession now?"
"It has not been out of my possession at any time since it was given to me," was the startling reply.
"Then how do you account for this photograph?"
"I don't account for it."
"But Dr. Loyd-the dagger-I had it in my hands," Hatch interposed in bewilderment.
"You are mistaken," replied the Turk quietly. "It is still in my possession."