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?"

CHAPTER IV

MADEMOISELLE DORIAN

The telephone bell rang.

Stuart reached across for the instrument and raised the receiver. "Yes," he said—"Dr. Stuart speaking. Inspector Dunbar is here. Hold on."

He passed the instrument to Dunbar, who had stood up on hearing his name mentioned. "Sergeant Sowerby at Scotland Yard wishes to speak to you, Inspector."

"Hullo," said Dunbar—"that you, Sowerby. Yes—but I arrived here only a short time ago. What's that?—Max? Good God! what does it all mean! Are you sure of the number—49685? Poor chap—he should have worked with us instead of going off alone like that. But he was always given to that sort of thing. Wait for me. I'll be with you in a few minutes. I can get a taxi. And, Sowerby—listen! It's 'The Scorpion' case right enough. That bit of gold found on the dead man is not a cactus stem; it's a scorpion's tail!"

He put down the telephone and turned to Stuart, who had been listening to the words with growing concern. Dunbar struck his open palm down on to the table with a violent gesture.

"We have been asleep!" he exclaimed. "Gaston Max of the Paris Service has been at work in London for a month, and we didn't know it!"

"Gaston Max!" cried Start—"then it must be a big case indeed."

As a student of criminology the name of the celebrated Frenchman was familiar to him as that of the foremost criminal investigator in Europe, and he found himself staring at the fragment of gold with a new and keener interest.

"Poor chap," continued Dunbar—"it was his last. The body brought in from Hanover Hole has been identified as his."

"What! it is the body of Gaston Max!"

"Paris has just wired that Max's reports ceased over a week ago. He was working on the case of Sir Frank Narcombe, it seems, and I never knew! But I predicted a long time ago that Max would play the lone-hand game once too often. They sent particulars. The identification disk is his. Oh! there's no doubt about it, unfortunately. The dead man's face is unrecognizable, but it's not likely there are two disks of that sort bearing the initials G.M. and the number 49685. I'm going along now. Should you care to come, doctor?"

"I am expecting a patient, Inspector," replied Stuart—"er—a special case. But I hope you will keep me in touch with this affair?"

"Well, I shouldn't have suggested your coming to the Yard if I hadn't wanted to do that. As a matter of fact, this scorpion job seems to resolve itself into a case of elaborate assassination by means of some unknown poison; and although I should have come to see you in any event, because you have helped me more than once, I came to-night at the suggestion of the Commissioner. He instructed me to retain your services if they were available."

"I am honoured," replied Stuart. "But after all, Inspector, I am merely an ordinary suburban practitioner. My reputation has yet to be made. What's the matter with Halesowen of Upper Wimpole Street? He's the big man."

"And if Sir Frank Narcombe was really poisoned—as Paris seems to think he was—he's also a big fool." retorted Dunbar bluntly. "He agreed that death was due to heart trouble."

"I know he did; unsuspected ulcerative endocarditis. Perhaps he was right."

"If he was right," said Dunbar, taking up the piece of gold from the table, "what was Gaston Max doing with this thing in his possession?"

"There may be no earthly connection between Max's inquiries and the death of Sir Frank."

"On the other hand—there may! Leaving Dr. Halesowen out of the question, are you open to act as expert adviser in this case?"

"Certainly; delighted."

"Your fee is your own affair, doctor. I will communicate with you later, if you wish, or call again in the morning."

Dunbar wrapped up the scorpion's tail in the piece of tissue paper and was about to replace it in his note-case. Then:

"I'll leave this with you, doctor," he said. "I know it will be safe enough, and you might like to examine it at greater leisure."

"Very well," replied Stuart. "Some of the engraving is very minute.
I will have a look at it through a glass later."

He took the fragment from Dunbar, who had again unwrapped it, and, opening a drawer of the writing-table in which he kept his cheque-book and some few other personal valuables, he placed the curious piece of gold-work within and relocked the drawer.

"I will walk as far as the cab-rank with you," he said, finding himself to be possessed of a spirit of unrest. Whereupon the two went out of the room, Stuart extinguishing the lamps as he came to the door.

They had not left the study for more than two minutes ere a car drew up outside the house, and Mrs. M'Gregor ushered a lady into the room but lately quitted by Stuart and Dunbar, turning up the lights as she entered.

"The doctor has gone out but just now, Miss Dorian," she said stiffly. "I am sorry that ye are so unfortunate in your veesits. But I know he'll be no more than a few minutes."

The girl addressed was of a type fully to account for the misgivings of the shrewd old Scotswoman. She had the slim beauty of the East allied to the elegance of the West. Her features, whilst cast in a charming European mould, at the same time suggested in some subtle way the Oriental. She had the long, almond-shaped eyes of the Egyptian, and her hair, which she wore unconventionally in a picturesque fashion reminiscent of the harem, was inclined to be "fuzzy," but gleamed with coppery tints where the light touched its waves.

She wore a cloak of purple velvet having a hooded collar of white fox fur; it fastened with golden cords. Beneath it was a white and gold robe, cut with classic simplicity of line and confined at the waist by an ornate Eastern girdle. White stockings and dull gold shoes exhibited to advantage her charming little feet and slim ankles, and she carried a handbag of Indian beadwork. Mlle. Dorian was a figure calculated to fire the imagination of any man and to linger long and sweetly in the memory.

Mrs. M'Gregor, palpably ill at ease, conducted her to an armchair.

"You are very good," said the visitor, speaking with a certain hesitancy and with a slight accent most musical and fascinating. "I wait a while if I may."

"Dear, dear," muttered Mrs. M'Gregor, beginning to poke the fire, "he has let the fire down, of course! Is it out? No … I see a wee sparkie!"

She set the poker upright before the nearly extinguished fire and turned triumphantly to Mlle. Dorian, who was watching her with a slight smile.

"That will be a comforting blaze in a few minutes, Miss Dorian," she said, and went towards the door.

"If you please," called the girl, detaining her—"do you permit me to speak on the telephone a moment? As Dr.