the
interval, yet you tell me that Sergeant Sowerby communicated this
information to you, by telephone, half an hour ago."

Dunbar was tapping his teeth with the pencil. His amazement was too
great for words.

"Had the message been a false one," continued the Commissioner, "the
matter would have been resolved into a meaningless hoax, but the
message having been what it was, we find ourselves face to face with
no ordinary problem. Remember, Inspector, that voices on the telephone
are deceptive. Sergeant Sowerby has marked vocal mannerisms----"

"Which would be fairly easy to imitate? Yes, sir--that's so."

"But it brings us no nearer to the real problems; viz., first, the
sender of the message; and, second, his purpose."

There was a dull purring sound and the Assistant Commissioner raised
the telephone.

"Yes. Who is it that wishes to speak to him? Dr. Keppel Stuart?
Connect with my office."

He turned again to Dunbar.

"Dr. Stuart has a matter of the utmost urgency to communicate,
Inspector. It was at the house of Dr. Stuart, I take it, that you
received the unexplained message?"

"It was--yes."

"Did you submit to Dr. Stuart the broken gold ornament?"

"Yes. It's a scorpion's tail."

"Ah!" The Assistant Commissioner smiled satanically and lighted a
fresh cigarette. "And is Dr. Stuart agreeable to placing his unusual
knowledge at our disposal for the purposes of this case?"

"He is, sir."

The purring sound was repeated.

"You are through to Dr. Stuart," said the Assistant Commissioner.

"Hullo" cried Dunbar, taking up the receiver--"is that Dr. Stuart?
Dunbar speaking."

He stood silent for a while, listening to the voice over the wires.
Then: "You want me to come around now, doctor? Very well. I'll be
with you in less than half an hour."

He put down the instrument.

"Something extraordinary seems to have taken place at Dr. Stuart's
house a few minutes after I left, sir," he said. "I'm going back
there, now, for particulars. It sounds as though the 'phone message
might have been intended to get me away." He stared down at the
pencilled slip which the Assistant Commissioner had handed him, but
stared vacantly, and: "Do you mind if I call someone up, sir?" he
asked. "It should be done at once."

"Call by all means, Inspector."

Dunbar again took up the telephone.

"Battersea 0996," he said, and stood waiting. Then:

"Is that Battersea 0996?" he asked. "Is Dr. Stuart there? He is
speaki