shortcomings, and knew in his heart that he could never give her in charge of the police. More and more the wonder of it all grew upon him, and now he suddenly found himself thinking of the unexplained incident of the previous night.

"You do not answer," he said. "I will ask you another question: have you attempted to open that drawer prior to this evening?"

Mlle. Dorian looked up rapidly, and her cheeks, which had been pale, now flushed rosily.

"I try twice before," she confessed, "and cannot open it."

"Ah! And—has someone else tried also?"

Instantly her colour fled again, and she stared at him wide-eyed, fearful.

"Someone else?" she whispered.

"Yes—someone else. A man … wearing a sort of cowl——"

"Oh?" she cried and threw out her hands in entreaty. "Do not ask me of him! I dare not answer—I dare not!"

"You have answered," said Stuart, in a voice unlike his own; for a horrified amazement was creeping upon him and supplanting the contemptuous anger which the discovery of this beautiful girl engaged in pilfering his poor belongings had at first aroused.

The mystery of her operations was explained—explained by a deeper and a darker mystery. The horror of the night had been no dream but an almost incredible reality. He now saw before him an agent of the man in the cowl; he perceived that he was in some way entangled in an affair vastly more complex and sinister than a case of petty larceny.

"Has the golden scorpion anything to do with the matter?" he demanded abruptly.

And in the eyes of his beautiful captive he read the answer. She flinched again as she had done when he had taunted her with being a thief; but he pressed his advantage remorselessly.

"So you were concerned in the death of Sir Frank Narcombe!" he said.

"I was not!" she cried at him fiercely, and her widely opened eyes were magnificent. "Sir Frank Narcombe is——"

She faltered—and ceased speaking, biting her lip which had become tremulous again.

"Sir Frank Narcombe is?" prompted Stuart, feeling himself to stand upon the brink of a revelation.

"I know nothing of him—this Sir Frank Narcombe."

Stuart laughed unmirthfully.

"Am I, by any chance, in danger of sharing the fate of that distinguished surgeon?" he asked.

His question produced an unforeseen effect. Mlle. Dorian suddenly rested her jewelled hands upon his shoulders, and he found himself looking hungrily into those wonderful Eastern eyes.

"If I swear that I speak the truth, will you believe me?" she whispered, and her fingers closed convulsively upon his shoulders.

He was shaken. Her near presence was intoxicating. "Perhaps," he said unsteadily.

"Listen, then. Now you are in danger, yes. Before, you were not, but now you must be very careful. Oh! indeed, indeed, I tell you true! I tell you for your own sake. Do with me what you please. I do not care. It does not matter. You ask me why I come here. I tell you that also. I come for what is in the long envelope—look, I cannot hide it. It is on the fire!"

Stuart turned and glanced toward the grate. A faint wisp of brown smoke was arising from a long white envelope which lay there. Had the fire been actually burning, it must long ago have been destroyed. More than ever mystified, for the significance of the envelope was not evident to him, he ran to the grate and plucked the smouldering paper from the embers.

As he did so, the girl, with one quick glance in his direction, snatched her cloak, keys and bag and ran from the room. Stuart heard the door close, and racing back to the table he placed the slightly charred envelope there beside the fragment of gold and leapt to the door.

"Damn!" he said.

His escaped prisoner had turned the key on the outside. He was locked in his own study!

Momentarily nonplussed, he stood looking at the closed door. The sound of a restarted motor from outside the house spurred him to action. He switched off the lamps, crossed the darkened room and drew back the curtain, throwing open the French windows. Brilliant moonlight bathed the little lawn with its bordering of high privet hedges. Stuart ran out as the sound of the receding car reached his ears. By the time that he had reached the front of the house the street was vacant from end to end. He walked up the steps to the front door, which he unfastened with his latch-key. As he entered the hall, Mrs. M'Gregor appeared from her room.

"I did no' hear ye go out with Miss Dorian," she said.

"That's quite possible, Mrs. M'Gregor, but she has gone, you see."

"Now tell me, Mr. Keppel, did ye or did ye no' hear the wail o' the pibroch the night?

"No—I am afraid I cannot say that I did, Mrs. M'Gregor," replied Stuart patiently. "I feel sure you must be very tired and you can justifiably turn in now. I am expecting no other visitor. Good-night."

Palpably dissatisfied and ill at ease, Mrs. M'Gregor turned away.

"Good-night, Mr. Keppel," she said.

Stuart, no longer able to control his impatience, hurried to the study door, unlocked it and entered. Turning on the light, he crossed and hastily drew the curtains over the window recess, but without troubling to close the window which he had opened. Then he returned to the writing-table and took up the sealed envelope whose presence in his bureau was clearly responsible for the singular visitation of the cowled man and for the coming of the lovely Mlle. Dorian.

The "pibroch of the M'Gregors": He remembered something—something which, unaccountably, he hitherto had failed to recall: that fearful wailing in the night—which had heralded the coming of the cowled man!—or had it been a signal of some kind?

He stared at the envelope blankly, then laid it down and stood looking for some time at the golden scorpion's tail. Finally, his hands resting upon the table, he found that almost unconsciously he had been listening—listening to the dim night sounds of London and to the vague stirrings within the house.

"Now, you are in danger. Before, you were not…."

Could he believe her? If in naught else, in this at least surely she had been sincere? Stuart started—then laughed grimly.

A clock on the mantel-piece had chimed the half-hour.

CHAPTER VI

THE ASSISTANT COMMISSIONER

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.