Seating himself at the writing-table, Stuart began mechanically to arrange his papers. Then from the tobacco jar he loaded his pipe, but his manner remained abstracted. Yet he was not thinking of the phantom piper but of Mlle. Dorian.  
Until he had met this bewilderingly pretty woman he had thought that his heart was for evermore proof against the glances of bright eyes. Mademoiselle had disillusioned him. She was the most fragrantly lovely creature he had ever met, and never for one waking moment since her first visit, had he succeeded in driving her bewitching image from his mind. He had tried to laugh at his own folly, then had grown angry with himself, but finally had settled down to a dismayed acceptance of a wild infatuation.
 
He had no idea who Mlle. Dorian was; he did not even know her exact nationality, but he strongly suspected there was a strain of Eastern blood in her veins. Although she was quite young, apparently little more than twenty years of age, she dressed like a woman of unlimited means, and although all her visits had been at night he had had glimpses of the big car which had aroused Mrs. M'Gregor's displeasure.
 
Yes—so ran his musings, as, pipe in mouth, he rested his chin in his hands and stared grimly into the fire—she had always come at night and always alone. He had supposed her to be a Frenchwoman, but an unmarried French girl of good family does not make late calls, even upon a medical man, unattended. Had he perchance unwittingly made himself a party to the escapade of some unruly member of a noble family? From the first he had shrewdly suspected the ailments of Mlle. Dorian to be imaginary—Mlle. Dorian? It was an odd name.
 
"I shall be imagining she is a disguised princess if I wonder about her any more!" he muttered angrily.
 
Detecting himself in the act of heaving a weary sigh, he coughed in self-reproval and reached into a pigeon-hole for the MS. of his unfinished paper on "Snake Poisons and Their Antidotes." By chance he pulled out the brief account, written the same morning, of his uncanny experience during the night. He read it through reflectively.
 
It was incomplete. A certain mental haziness which he had noted upon awakening had in some way obscured the facts. His memory of the dream had been imperfect. Even now, whilst recognizing that some feature of the experience was missing from his written account, he could not identify the omission. But one memory arose starkly before him—that of the cowled man who had stood behind the curtains. It had power to chill him yet. The old incredulity returned and methodically he re-examined the contents of some of the table drawers. Ere long, however, he desisted impatiently.
 
"What the devil could a penniless doctor have hidden in his desk that was worth stealing!" he said aloud. "I must avoid cold salmon and cucumber in future."
 
He tossed the statement aside and turned to his scientific paper.
 
There came knock at the door.
 
"Come in!" snapped Stuart irritably; but the next moment he had turned, eager-eyed to the servant who had entered.
 
"Inspector Dunbar has called, sir."
 
"Oh, all right," said Stuart, repressing another sigh. "Show him in here."
 
There entered, shortly, a man of unusual height, a man gaunt and square both of figure and of face. He wore his clothes and his hair untidily. He was iron grey and a grim mouth was ill concealed by the wiry moustache. The most notable features of a striking face were the tawny leonine eyes, which could be fierce, which could be pensive and which were often kindly.
 
"Good evening, doctor," he said—and his voice was pleasant and unexpectedly light in tome. "Hope I don't intrude."
 
"Not at all, Inspector," Stuart assured him.
 
"Make yourself comfortable in the armchair and fill your pipe."
 
"Thanks," said Dunbar. "I will." He took out his pipe and reached out a long arm for the tobacco jar. "I came to see if you could give me a tip on a matter that has cropped up."
 
"Something in my line?" asked Stuart, a keen professional look coming momentarily into his eyes.
 
"It's supposed to be a poison case, although I can't see it myself," answered the detective—to whom Keppel Stuart's unusual knowledge of poisons had been of service in the past; "but if what I suspect is true, it's a very big case all the same."
 
Laying down his pipe, which he had filled but not lighted, Inspector Dunbar pulled out from the inside pocket of his tweed coat a bulging note-book and extracted therefrom some small object wrapped up in tissue paper. Unwrapping this object, he laid it upon the table.
 
"Tell me what that is, doctor," he said, "and I shall be obliged."
 
Stuart peered closely at that which lay before him. It was a piece of curiously shaped gold, cunningly engraved in a most unusual way. Rather less than an inch in length, it formed a crescent made up of six oval segments joined one to another, the sixth terminating in a curled point. The first and largest segment ended jaggedly where it had evidently been snapped off from the rest of the ornament—if the thing had formed part of an ornament. Stuart looked up, frowning in a puzzled way.
 
"It is a most curious fragment of jewellery—possibly of Indian origin," he said.
 
Inspector Dunbar lighted his pipe and tossed the match-end into the fire. "But what does it represent?" he asked.
 
"Oh, as to that—I said a curious fragment advisedly, because I cannot imagine any woman wearing such a beastly thing. It is the tail of a scorpion."
 
"Ah!" cried Dunbar, the tawny eyes glittering with excitement. "The tail of a scorpion! I thought so! And Sowerby would have it that it represented the stem of a Cactus or Prickly Pear!"
 
"Not so bad a guess," replied Stuart. "There are resemblances—not in the originals but in such a miniature reproduction as this. He was wrong, however. May I ask where you obtained the fragment?"
 
"I'm here to tell you, doctor, for now that I know it's a scorpion's tail I know that I'm out of my depth as well. You've travelled in the East and lived in the East—two very different things. Now, while you were out there, in India, China, Burma, and so on, did you ever come across a religion or a cult that worshipped scorpions?"
 
Stuart frowned thoughtfully, rubbing his chin with the mouthpiece of his pipe. Dunbar watched him expectantly.
 
"Help yourself to whiskey-and-soda, Inspector," said Stuart absently.
"You'll find everything on the side-table yonder. I'm thinking."
 
Inspector Dunbar nodded, stood up and crossed the room, where he busied himself with syphon and decanter. Presently he returned, carrying two full glasses, one of which he set before Stuart. "What's the answer, doctor?" he asked.
 
"The answer is no. I am not acquainted with any sect of scorpion-worshippers, Inspector. But I once met with a curious experience at Su-Chow in China, which I have never been able to explain, but which may interest you. It wanted but a few minutes to sunset, and I was anxious to get back to my quarters before dusk fell. Therefore I hurried up my boy, who was drawing the rickshaw, telling him to cross the Canal by the Wu-men Bridge. He ran fleetly in that direction, and we were actually come to the steep acclivity of the bridge, when suddenly the boy dropped the shafts and fell down on his knees, hiding his face in his hands.
 
"'Shut your eyes tightly, master!' he whispered. 'The Scorpion is coming!'
 
"I stared down at him in amazement, as was natural, and not a little angrily; for his sudden action had almost pitched me on my head. But there he crouched, immovable, and staring up the slope I say that it was entirely deserted except for one strange figure at that moment crossing the crown of the bridge and approaching. It was the figure of a tall and dignified Chinaman, or of one who wore the dress of a Chinaman. For the extra-ordinary thing about the stranger's appearance was this; he also wore a thick green veil!"
 
"Covering his face?"
 
"So as to cover his face completely. I was staring at him in wonder, when the boy, seeming to divine the other's approach, whispered, 'Turn your head away! Turn your head away!"
 
"He was referring to the man with the veil?"
 
"Undoubtedly. Of course I did nothing of the kind, but it was impossible to discern the stranger's features through the thick gauze, although he passed quite close to me. He had not proceeded another three paces, I should think, before my boy had snatched up the shafts and darted across the bridge as though all hell were after him! Here's the odd thing, though; I could never induce him to speak a word on the subject afterwards! I bullied him and bribed him, but all to no purpose. And although I must have asked more than a hundred Chinamen in every station of society from mandarin to mendicant, 'Who or what is The Scorpion?' one and all looked stupid, blandly assuring me that they did not know what I meant."
 
"H'm!" said Dunbar, "it's a queer yarn, certainly. How long ago would that be, doctor?"
 
"Roughly—five years."
 
"It sounds as though it might belong to the case. Some months back, early in the winter, we received instructions at the Yard to look out everywhere in the press, in buffets, theatres, but particularly in criminal quarters, for any reference (of any kind whatever) to a scorpion. I was so puzzled that I saw the Commissioner about it, and he could tell me next to nothing. He said the word had come through from Paris, but that Paris seemed to know no more about it than we did. It was associated in some way with the sudden deaths of several notable public men about that time; but as there was no evidence of foul play in any of the cases, I couldn't see what it meant at all. Then, six weeks ago, Sir Frank Narcombe, the surgeon, fell dead in the foyer of a West-End theatre—you remember?"