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. "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.