er a portion of
your domain which, so far, has escaped my inspection."

The doctor shrugged his shoulders.

"It is hardly a shooting gallery, but since it is so far removed from
the living portion of the house we sometimes use it for that purpose,"
he said. "I have not the slightest objection to your descending."

T. B. entered the lift. It was in darkness, as a result of Poltavo's
precautions.

"I will go alone," said T. B., and Fall, with a little bow, closed the
gates, and the lift descended.

They waited some time; Fall had the power, from where he was, of closing
the gates below and bringing the lift up again. This Poltavo knew to his
cost, but there were good reasons why the doctor should not exercise his
knowledge, and in a few minutes the lift came back to its original
position and T. B. stepped out.

"Thank you, I have learned all I want to know," he said with a keen
glance at Poltavo. "Really, you have an extraordinary house, Dr. Fall."

"It is always open to your inspection," said the doctor, with a heavy
smile.

T. B. was fingering the little electric lamp, which he carried in his
hand, in an absent-minded manner. Presently he put it into his pocket,
and, with a nod to his host, walked across the hall. He turned suddenly
and addressed Poltavo.

"When you were trapped in this house," he said, quietly, "and expected
considerable trouble in escaping from the trap, you took the precaution,
like the careful man that you are, of inscribing a message which might
aid those who came to your relief. This message has now served its
purpose," he smiled, as he saw the look of consternation on Poltavo's
face, "and you will be well advised to invite your friend to wipe it
out"; and with another nod he passed from the house, followed by his
three men.

"What does this mean?" asked Fall, quickly.

"I--I--" stammered Poltavo, flustered for once in his life, "wrote on
the side of the lift a few words only, nothing incriminating, my dear
doctor, just a line to say that I was imprisoned below."

With a curse Fall dashed into the little elevator.

"Bring a light," he said, and struck a match to read the scrawl which
Poltavo had written. Fortunately there was nothing in it which betrayed
the great secret of the house, but it was enough, as he realized, to
awaken the dormant suspicion, even supposing it was dormant, of this
indefatigable detective.

"You have made a nice mess of things," he said to Poltavo, sternl