x-Raythwaite was exactly where Mr. Tertius had left him in
the morning, when the two visitors were ushered into his laboratory. And
for the second time that day he listened in silence to Mr. Tertius's
story. When it was finished, he looked at Mr. Halfpenny, whose solemn
countenance had grown more solemn than ever.

"Queer story, isn't it, Halfpenny?" he said laconically. "How does it
strike you?"

Mr. Halfpenny slowly opened his pursed-up lips.

"Queer?" he exclaimed. "God bless me!--I'm astounded! I--but let me see
these--these things."

"Sealed 'em up not so long ago--just after lunch," remarked the
Professor, lifting his heavy bulk out of his chair. "But you can see 'em
all right through the glass. There you are!" He led the way to a
side-table and pointed to the hermetically-sealed receptacles in which
he had safely bestowed the tumbler and the sandwich brought so gingerly
from Portman Square by Mr. Tertius. "The tumbler," he continued, jerking
a big thumb at it, "will have, of course, to be carefully examined by an
expert in finger-prints; the sandwich, so to speak, affords primary
evidence. You see--what there is to see, Halfpenny?"

Mr. Halfpenny adjusted his spectacles, bent down, and examined the
exhibits with scrupulous, absorbed interest. Again he pursed up his
lips, firmly, tightly, as if he would never open them again; when he did
open them it was to emit a veritable whistle which indicated almost as
much delight as astonishment. Then he clapped Mr. Tertius on the back.

"A veritable stroke of genius!" he exclaimed. "Tertius, my boy, you
should have been a Vidocq or a Hawkshaw! How did you come to think of
it? For I confess that with all my forty years' experience of Law,
I--well, I don't think I should ever have thought of it!"

"Oh, I don't know," said Mr. Tertius, modestly. "I--well, I looked--and
then, of course, I saw. That's all!"

Mr. Halfpenny sat down and put his hands on his knees.

"It's a good job you did see, anyway," he said, ruminatively; "an
uncommonly good job. Well--you're certain of what we may call the
co-relative factor to what is most obvious in that sandwich?"

"Absolutely certain," replied Mr. Tertius.

"And you're equally certain about the diamond ring?"

"Equally and positively certain!"

"Then," said Mr. Halfpenny, rising with great decision, "there is only
one thing to be done. You and I, Tertius, must go at once--at once!--to
New Scotland Yard. In fact, we will dr