"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.