On the following morning Inspector Dunbar, having questioned Mrs. M'Gregor respecting the car in which Mlle. Dorian had visited the house and having elicited no other evidence than that it was "a fine luxurious concern," the Inspector and Dr. Stuart prepared to set out upon gruesome business. Mrs. M'Gregor was very favourably impressed with the Inspector. "A grand, pairsonable body," she confided to Stuart. "He'd look bonny in the kilt."  
To an East-End mortuary the cab bore them, and they were led by a constable in attendance to a stone-paved, ill-lighted apartment in which a swathed form lay upon a long deal table. The spectacle presented, when the covering was removed, was one to have shocked less hardened nerves than those of Stuart and Dunbar; but the duties of a police officer, like those of a medical man, not infrequently necessitate such inspections. The two bent over the tragic flotsam of the Thames unmoved and critical.
 
"H'm," said Stuart—"he's about the build, certainly. Hair iron-grey and close cropped and he seems to have worn a beard. Now, let us see."
 
He bent, making a close inspection of the skull; then turned and shook his head.
 
"No, Inspector," he said definitely. "This is not the cabman. There is no wound corresponding to the one which I dressed."
 
"Right," answered Dunbar, covering up the ghastly face. "That's settled."
 
"You were wrong, Inspector. It was not Gaston Max who left the envelope with me."
 
"No," mused Dunbar, "so it seems."
 
"Your theory that Max, jealously working alone, had left particulars of his inquiries, and clues, in my hands, knowing that they would reach Scotland Yard in the event of his death, surely collapsed when the envelope proved to contain nothing but a bit of cardboard?"
 
"Yes—I suppose it did. But it sounded so much like Max's round-about methods. Anyway I wanted to make sure that the dead man from Hanover Hole and your mysterious cabman were not one and the same."
 
Stuart entertained a lively suspicion that Inspector Dunbar was keeping something up his sleeve, but with this very proper reticence he had no quarrel, and followed by the constable, who relocked the mortuary behind them, they came out into the yard where the cab waited which was to take them to Scotland Yard. Dunbar, standing with one foot upon the step of the cab, turned to the constable.
 
"Has anyone else viewed the body?" he asked.
 
"No sir."
 
"No one is to be allowed to do so—you understand?—no one, unless he has written permission from the Commissioner."
 
"Very good, sir."
 
Half an hour later they arrived at New Scotland Yard and went up to Dunbar's room. A thick-set, florid man of genial appearance, having a dark moustache, a breezy manner and a head of hair resembling a very hard-worked blacking-brush, awaited them. This was Detective-Sargeant Sowerby with whom Stuart was already acquainted.
 
"Good-morning, Sergeant Sowerby," he said.
 
"Good-morning, sir. I hear that someone was pulling your leg last night."
 
"What do you mean exactly, Sowerby?" inquired Dunbar, fixing his fierce eyes upon his subordinate.
 
Sergeant Sowerby exhibited confusion.
 
"I mean nothing offensive, Inspector. I was referring to the joker who gave so good an imitation of my voice that even you were deceived."
 
"Ah," replied Dunbar—"I see. Yes—he did it well. He spoke just like you. I could hardly make out a word he said."
 
With this Caledonian shaft and a side-glance at Stuart, Inspector
Dunbar sat down at the table.
 
"Here's Dr. Stuart's description of the missing cabman," he continued, taking out his note-book. "Dr. Stuart has viewed the body and it is not the man. You had better take a proper copy of this."
 
"Then the cabman wasn't Max?" cried Sowerby eagerly. "I thought not."
 
"I believe you told me so before," said Dunbar sourly. "I also seem to recall that you thought a scorpion's tail was a Prickly Pear. However—here, on the page numbered twenty-six, is a description of the woman known as Mlle. Dorian. It should be a fairly easy matter to trace the car through the usual channels, and she ought to be easy to find, too."
 
He glanced at his watch. Stuart was standing by the lofty window looking out across the Embankment.
 
"Ten o'clock," said Dunbar. "The Commissioner will be expecting us."
 
"I am ready," responded Stuart.
 
Leaving Sergeant Sowerby seated at the table studying the note-book,
Stuart and Dunbar proceeded to the smoke-laden room of the Assistant
Commissioner. The great man, suavely satanic, greeted Stuart with
that polished courtesy for which he was notable.
 
"You have been of inestimable assistance to us in the past, Dr. Stuart," he said, "and I feel happy to know that we are to enjoy the aid of your special knowledge in the present case. Will you smoke one of my cigarettes? They are some which a friend is kind enough to supply to me direct from Cairo, and are really quite good."
 
"Thanks," replied Stuart. "May I ask in what direction my services are likely to prove available?"
 
The Commissioner lighted a fresh cigarette. Then from a heap of correspondence he selected a long report typed upon blue foolscap.
 
"I have here," he said, "confirmation of the telegraphic report received last night. The name of M. Gaston Max will no doubt be familiar to you?"
 
Stuart nodded.
 
"Well," continued the Commissioner, "it appears that he has been engaged in England for the past month endeavouring to trace the connection which he claims to exist between the sudden deaths of various notable people, recently—a list is appended—and some person or organisation represented by, or associated with, a scorpion. His personal theory not being available—poor fellow, you have heard of his tragic death—I have this morning consulted such particulars as I could obtain respecting these cases. If they were really cases of assassination, some obscure poison was the only mode of death that could possibly have been employed. Do you follow me?"
 
"Perfectly."
 
"Now, the death of Gaston Max under circumstances not yet explained, would seem to indicate that his theory was a sound one. In other words, I am disposed to believe that he himself represents the most recent outrage of what we will call 'The Scorpion.' Even at the time that the body of the man found by the River Police had not been identified, the presence upon his person of a fragment of gold strongly resembling the tail of a scorpion prompted me to instruct Inspector Dunbar to consult you. I had determined upon a certain course. The identification of the dead man with Gaston Max merely strengthens my determination and enhances the likelihood of my idea being a sound one."
 
He flicked the ash from his cigarette and resumed:
 
"Without mentioning names, the experts consulted in the other cases which—according to the late Gaston Max—were victims of 'The Scorpion,' do not seem to have justified their titles. I am arranging that you shall be present at the autopsy upon the body of Gaston Max. And now, permit me to ask you a question: are you acquainted with any poison which would produce the symptoms noted in the case of Sir Frank Narcombe, for instance?"
 
Stuart shook his head slowly.
 
"All that I know of the case," he said, "is that he was taken suddenly ill in the foyer of a West-End theatre, immediately removed to his house in Half Moon Street, and died shortly afterward. Can you give me copies of the specialists' reports and other particulars? I may then be able to form an opinion."
 
"I will get them for you," replied the Commissioner, the exact nature of whose theory was by no means evident to Stuart. He opened a drawer. "I have here," he continued, "the piece of cardboard and the envelope left with you by the missing cab-man. Do you think there is any possibility of invisible writing?"
 
"None," said Stuart confidently. "I have tested in three or four places as you will see by the spots, but my experiments will in no ............