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.

He walked out into the bare corridor and along to the room of the
Assistant Commissioner. Knocking upon the door, he opened it
immediat