Professor Deeping's number was in the telephone directory, therefore, on returning to my room, where there still lingered the faint perfume of my late visitor's presence, I asked for his number. He proved to be at home.  
"Strange you should ring me up, Cavanagh," he said; "for I was about to ring you up."
 
"First," I replied, "listen to the contents of an anonymous letter which I have received."
 
(I remembered, and only just in time, my promise to the veiled messenger.)
 
"To me," I added, having read him the note, "it seems to mean nothing. I take it that you understand better than I do."
 
"I understand very well, Cavanagh!" he replied. "You will recall my story of the scimitar which flashed before me in the darkness of my stateroom on the Mandalay? Well, I have seen it again! I am not an imaginative man: I had always believed myself to possess the scientific mind; but I can no longer doubt that I am the object of a pursuit which commenced in Mecca! The happenings on the steamer prepared me for this, in a degree. When the man lost his hand at Port Said I doubted. I had supposed the days of such things past. The attempt to break into my stateroom even left me still uncertain. But the outrage upon the steward at the docks removed all further doubt. I perceived that the contents of a certain brown leather case were the objective of the crimes."
 
I listened in growing wonder.
 
"It was not necessary in order to further the plan of stealing the bag that the hands were severed," resumed the Professor. "In fact, as was rendered evident by the case of the steward, this was a penalty visited upon any one who touched it! You are thinking of my own immunity?"
 
"I am!"
 
"This is attributable to two things. Those who sought to recover what I had in the case feared that my death en route might result in its being lost to them for ever. They awaited a suitable opportunity. They had designed to take it at Port Said certainly, I think; but the bag was too large to be readily concealed, and, after the outrage, might have led to the discovery of the culprit. In the second place, they are uncertain of my faith. I have long passed for a true Believer in the East! As a Moslem I visited Mecca—"
 
"You visited Mecca!"
 
"I had just returned from the hadj when I joined the Mandalay at Port Said! My death, however, has been determined upon, whether I be Moslem or Christian!"
 
"Why?"
 
"Because," came the Professor's harsh voice over the telephone, "of the contents of the brown leather case! I will not divulge to you now the nature of these contents; to know might endanger you. But the case is locked in my safe here, and the key, together with a full statement of the true facts of the matter, is hidden behind the first edition copy of my book 'Assyrian Mythology,' in the smaller bookcase—"
 
"Why do you tell me all this?" I interrupted.
 
He laughed harshly.
 
"The identity of my pursuer has just dawned upon me," he said. "I know that my life is in real danger. I would give up what is demanded of me, but I believe its possession to be my strongest safeguard."
 
Mystery upon mystery! I seemed to be getting no nearer to the heart of this maze. What in heaven's name did it all mean? Suddenly an idea struck me.
 
"Is our late fellow passenger, Mr. Ahmadeen, connected with the matter?" I asked.
 
"In no way," replied Deeping earnestly. "Mr. Ahmadeen is, I believe, a person of some consequence in the Moslem world; but I have nothing to fear from him."
 
"What steps have you taken to protect yourself?"
 
Again the short laugh reached my ears.
 
"I'm afraid long residence in the East has rendered me something of a fatalist, Cavanagh! Beyond keeping my door locked, I have taken no steps whatever. I fear I am quite accessible!"
 
A while longer we talked; and with every word the conviction was more strongly borne in upon me that some uncanny menace threatened the peace, perhaps the life, of Professor Deeping.
 
I had hung up the receiver scarce a moment when, acting upon a sudden determination, I called up New Scotland Yard, and asked for Detective-Inspector Bristol, whom I knew well. A few words were sufficient keenly to arouse his curiosity, and he announced his intention of calling upon me immediately. He was in charge of the case of the severed hand.
 
I made no attempt to resume work in the interval preceding his arrival. I had not long to wait, however, ere Bristol was ringing my bell; and I hurried to the door, only too glad to confide in one so well equipped to analyze my doubts and fears. For Bristol is no ordinary policeman, but a trained observer, who, when I first made his acquaintance, completely upset my ideas upon the mental limitations of the official detective force.
 
In appearance Bristol suggests an Anglo-Indian officer, and at the time of which I write he had recently returned from Jamaica and his face was as bronzed as a sailor's. One would never take Bristol for a detective. As he seated himself in the armchair, without preamble I plunged into my story. He listened gravely.
 
"What sort of house is Professor Deeping's?" he asked suddenly.
 
"I have no idea," I replied, "beyond the fact that it is somewhere in Dulwich."
 
"May I use your telephone?"
 
"Certainly."
 
Very quickly Bristol got into communication with the superintendent of P Division. A brief delay, and the man came to the telephone whose beat included the road wherein Professor Deeping's house was situated.
 
"Why!" said Bristol, hanging up the receiver after making a number of inquiries, "it's a sort of rambling cottage in extensive grounds. There's only one servant, a manservant, and he sleeps in a detached lodge. If the Professor is really in danger of attack he could not well have chosen a more likely residence for the purpose!"
 
"What shall you do? What do you make of it all?"
 
"As I see the case," he said slowly, "it stands something like this: Professor Deeping has..."
 
The telephone bell began to ring.
 
I took up the receiver.
 
"Hullo! Hullo."
 
"Cavanagh!—is that Cavanagh?"
 
"Yes! yes! who is that?"
 
"Deeping! I have rung up the police, and they are sending some one. But I wish..."
 
His voice trailed off. The sound of a confused and singular uproar came to me.
 
"Hullo!" I cried. "Hullo!"
 
A shriek—a deathful, horrifying cry—and a distant babbling alone answered me. There was a crash. Clearly, Deeping had dropped the receiver. I suppose my face blanched.
 
"What is it?" asked Bristol anxiously.
 
"God knows what it is!" I said. "Deeping has met with some mishap—"
 
When, over the wires—
 
"Hassan of Aleppo!" came a dying whisper. "Hassan ... of Aleppo..."