as a way out of every dilemma. I determined to
learn something of these rappings."

Craig paused and glanced first at Farrington, then at Mrs. Popper, and
then at Mr. Vandam.

"Mr. Jameson," he resumed, "will escort the doctor, the inspector, Mr.
Farrington, Mrs. Popper, and Mr. Vandam into my imitation hall of the
Vandam mansion. I want each of you in turn to tiptoe up that hall to a
spot indicated on the wall, back of the cabinet, and strike that spot
several sharp blows with your knuckles."

I did as Craig instructed tiptoeing up myself first so that they could
not mistake his meaning. The rest followed separately, and after a
moment we returned silently in suppressed excitement to the room.

Craig was still standing by the table, but now the pendulums with the
magnets and needles and the drums worked by clockwork were before him.

"Another person outside the Vandam family had a key to the Vandam
mansion," he began gravely. "That person, by the way, was the one who
waited, night by night, until Mrs. Vandam took the fatal capsule,
and then when she had taken it apprised the old man of the fact and
strengthened an already blind faith in the shadow world."

You could have heard a pin drop. In fact you could almost have felt it
drop.

"That other person who, unobserved, had free access to the house," he
continued in the breathless stillness, "is in this room now."

He was looking at O'Connor as if for corroboration. O'Connor nodded.
"Information derived from the butler," he muttered.

"I did not know this until yesterday," Kennedy continued, "but I
suspected that something of the sort existed when I was first told by
Dr. Hanson of the rappings. I determined to hear those rappings, and
make a record of them. So, the night Mr. Jameson and I visited Mr.
Vandam, I carried this little instrument with me."

Almost lovingly he touched the pendulums on the table. They were now
at rest and kept so by means of a lever that prevented all vibration
whatever.

"See, I release this lever--now, let no one in the room move. Watch
the needles on the paper as the clockwork revolves the drums. I take a
step--ever so lightly. The pendulums vibrate, and the needles trace a
broken line on the paper on each drum. I stop; the lines are practically
straight. I take another step and another, ever so lightly. See the
delicate pendulums vibrate? See, the lines they trace are jagged lines."

He stripped the paper off the drums and laid