intensity of the emotions by recording their effects on the heart
and lungs together. The truth can literally be tapped, even where
no confession can be extracted. A moment's glance at this line,
traced here by each of you, can tell the expert more than words."

"Then it was a mushroom that poisoned Jack!" interrupted Lewis,
suddenly. "Some poisonous Amanita got mixed with the edible
mushrooms?"

Kennedy answered, quickly, without taking his eyes off the line
the needle was tracing:

"No; this was a case of the deliberate use of the active principle
itself, muscarin--with the expectation that the death, if the
cause was ever discovered, could easily be blamed on such a
mushroom. Somehow--there were many chances--the poison was slipped
into the ramekin Francois was carefully preparing for Mansfield.
The method does not interest me so much as the fact--"

There was a slight noise from the other room where Mansfield lay.
Instantly we were all on our feet. Before any of us could reach
the door Helen Grey had slipped through it.

"Just a second," commanded Kennedy, extending the sequin toward us
to emphasize what he was about to say. "The poisoning and the
robbery were the work of one hand. That sequin is the key that has
unlocked the secret which my pneumograph has recorded. Some one
saw that robbery committed--knew nothing of the contemplated
poisoning to cover it. To save the reputation of the robber--at
any cost--on the spur of the moment the ruse of placing the sequin