Detective-Inspector Dunbar arrived at New Scotland Yard in a veritable fever of excitement. Jumping out of the cab he ran into the building and without troubling the man in charge of the lift went straight on upstairs to his room. He found it to be in darkness and switched on the green-shaded lamp which was suspended above the table. Its light revealed a bare apartment having distempered walls severely decorated by an etching of a former and unbeautiful Commissioner. The blinds were drawn. A plain, heavy deal table (bearing a blotting-pad, a pewter ink-pot, several pens and a telephone), together with three uncomfortable chairs, alone broke the expanse of highly polished floor. Dunbar glanced at the table and then stood undecided in the middle of the bare room, tapping his small, widely separated teeth with a pencil which he had absently drawn from his waistcoat pocket. He rang the bell.  
A constable came in almost immediately and stood waiting just inside the door.
 
"When did Sergeant Sowerby leave?" asked Dunbar.
 
"About three hours ago, sir."
 
"What!" cried Dunbar. "Three hours ago! But I have been here myself within that time—in the Commissioner's office."
 
"Sergeant Sowerby left before then. I saw him go."
 
"But, my good fellow, he has been back again. He spoke to me on the telephone less than a quarter of an hour ago."
 
"Not from here, sir."
 
"But I say it was from here!" shouted Dunbar fiercely; "and I told him to wait for me."
 
"Very good, sir. Shall I make inquiries?"
 
"Yes. Wait a minute. Is the Commissioner here?"
 
"Yes, sir, I believe so. At least I have not seen him go."
 
"Find Sergeant Sowerby and tell him to wait here for me," snapped
Dunbar.
 
He walked out into the bare corridor and along to the room of the Assistant Commissioner. Knocking upon the door, he opened it immediately, and entered an apartment which afforded a striking contrast to his own. For whereas the room of Inspector Dunbar was practically unfurnished, that of his superior was so filled with tables, cupboards, desks, bureaux, files, telephones, bookshelves and stacks of documents that one only discovered the Assistant Commissioner sunk deep in a padded armchair and a cloud of tobacco smoke by dint of close scrutiny. The Assistant Commissioner was small, sallow and satanic. His black moustache was very black and his eyes were of so dark a brown as to appear black also. When he smiled he revealed a row of very large white teeth, and his smile was correctly Mephistophelean. He smoked a hundred and twenty Egyptian cigarettes per diem, and the first and second fingers of either hand were coffee-coloured.
 
"Good-evening, Inspector," he said courteously. "You come at an opportune moment." He lighted a fresh cigarette. "I was detained here unusually late to-night or this news would not have reached us till the morning." He laid his finger upon a yellow form. "There is an unpleasant development in 'The Scorpion' case."
 
"So I gather, sir. That is what brought me back to the Yard."
 
The Assistant Commissioner glanced up sharply.
 
"What brought you back to the Yard?" he asked.
 
"The news about Max."
 
The assistant Commissioner leaned back in his chair. "Might I ask, Inspector," he said, "what news you have learned and how you have learned it?"
 
Dunbar stared uncomprehendingly.
 
"Sowerby 'phoned me about half an hour ago, sir. Did he do so without your instructions?"
 
"Most decidedly. What was his message?"
 
"He told me," replied Dunbar, in ever-growing amazement, "that the body brought in by the River Police last night had been identified as that of Gaston Max."
 
The Assistant Commissioner handed a pencilled slip to Dunbar. It read as follows:—
 
"Gaston Max in London. Scorpion, Narcombe. No report since 30th ult.
Fear trouble. Identity-disk G. M. 49685."
 
"But, sir," said Dunbar—"this is exactly what Sowerby told me!"
 
"Quite so. That is the really extraordinary feature of the affair. Because, you see, Inspector, I only finished decoding this message at the very moment that you knocked at my door!"
 
"But——"
 
"There is no room for a 'but,' Inspector. This confidential message from Paris reached me ten minutes ago. You know as well as I know that there is no possibility of leakage. No one has entered my room in the interval, yet you tell me that Sergeant Sowerby communicated this information to you, by telephone, half an hour ago."
 
Dunbar was tapping his teeth with the pencil. His amazement was too great for words.
 
"Had the message been a false one," continued the Commissioner, "the matter would have been resolved into a meaningless hoax, but the message having been what it was, we find ourselves face to face with no ordinary problem. Remember, Inspector, that voices on the telephone are deceptive. Sergeant Sowerby has marked vocal mannerisms——"
 
"Which would be fairly easy to imitate? Yes, sir—that's so."
 
"But it brings us no nearer to the real problems; viz., first, the sender of the message; and, second, his purpose."
 
There was a dull purring sound and the Assistant Commissioner raised the telephone.
 
"Yes. Who is it that wishes to speak to him? Dr. Keppel Stuart?
Connect with my office."
 
He turned again to Dunbar.
 
"Dr. Stuart has a matter of the utmost urgency to communicate, Inspector. It was at the house of Dr. Stuart, I take it, that you received the unexplained message?"
 
"It was—yes."
 
"Did you submit to Dr. Stuart the broken gold ornament?"
 
"Yes. It's a scorpion's tail."
 
"Ah!" The Assistant Commissioner smiled satanically and lighted a fresh cigarette. "And is Dr. Stuart agreeable to placing his unusual knowledge at our disposal for the purposes of this case?"
 
"He is, sir."
 
The purring sound was repeated.
 
"You are through to Dr. Stuart," said the Assistant Commissioner.
 
"Hullo" cried Dunbar, taking up the receiver—"is that Dr. Stuart?
Dunbar speaking."
 
He stood silent for a while, listening to the voice over the wires. Then: "You want me to come around now, doctor? Very well. I'll be with you in less than half an hour."
 
He put down the instrument.
 
"Something extraordinary seems to have taken place at Dr. Stuart's house a few minutes after I left, sir," he said. "I'm going back there, now, for particulars. It sounds as though the 'phone message might have been intended to get me away." He stared down at the pencilled slip which the Assistant Commissioner had handed him, but stared vacantly, and: "Do you mind if I call someone up, sir?" he asked. "It should be done at once."
 
"Call by all means, Inspector."
 
Dunbar again took up the telephone.
 
"Battersea 0996," he said, and stood waiting. Then:
 
"Is that Battersea 0996?" he asked. "Is Dr. Stuart there? He is speaking? Oh, this is Inspector Dunbar. You called me up here at the Yard a few moments ago, did you not? Correct, doctor; that's all I wanted to know. I am coming now."
 
"Good," said the Assistant Commissioner, nodding his approval. "You will have to check 'phone messages in that way until you have run your mimic to earth, Inspector. I don't believe for a moment that it was Sergeant Sowerby who rang you up at Dr. Stuart's."
 
"Neither do I," said Dunbar grimly. "But I begin to have a glimmer of a notion who it was. I'll be saying good-night, sir. Dr. Stuart seems to have something very important to tell me."
 
As a mere matter of form he waited for the report of the constable who had gone in quest of Sowerby, but it merely confirmed the fact that Sowerby had left Scotland Yard over three hours earlier. Dunbar summoned a taxicab and proceeded to the house of Dr. Stuart.