Lying on the floor he had grasped her foot and caught her heel with a firm hand.  She had responded with a wild yell that showed she knew she was trapped.  Her secret was out.

Hysterically Mrs. Popper began to upbraid the inspector as he rose to his feet, but Farrington quickly interposed.

“Something was working against us to-night, gentlemen.  Yet you demanded results.  And when the spirits will not come, what is she to do?  She forgets herself in her trance; she produces, herself, the things that you all could see supernaturally if you were in sympathy.”

The mere sound of Farrington’s voice seemed to rouse in me all the animosity of my nature.  I felt that a man who could trump up an excuse like that when a person was caught with the goods was capable of almost anything.

“Enough of this fake seance,” exclaimed Craig.  “I have let it go on merely for the purpose of opening the eyes of a certain deluded gentleman in this room.  Now, if you will all be seated I shall have something to say that will finally establish whether Mary Vandam was the victim of accident, suicide, or murder.”

With hearts beating rapidly we sat in silence.

Craig took the beakers and test-tubes from the shelf behind the curtain and placed them on the little deal table that had been so merrily dancing about the room.

“The increasing frequency with which tales of murder by poison appear in the newspapers,” he began formally, “is proof of how rapidly this new civilisation of ours is taking on the aspects of the older civilisations across the seas.  Human life is cheap in this country; but the ways in which human life has been taken among us have usually been direct, simple, aboveboard, in keeping with our democratic and pioneer traditions.  The pistol and the bowie-knife for the individual, the rope and the torch for the mob, have been the usual instruments of sudden death.  But when we begin to use poisons most artfully compounded in order to hasten an expected bequest and remove obstacles in its way—­well, we are practising an art that calls up all the memories of sixteenth century Italy.

“In this beaker,” he continued, “I have some of the contents of the stomach of the unfortunate woman.  The coroner’s physician has found that they show traces of morphine.  Was the morphine in such quantities as to be fatal?  Without doubt.  But equally without doubt analysis could not discover and prove it in the face of one inconsistency.  The usual test which shows morphine poisoning failed in this case.  The pupils of her eyes were not symmetrically contracted.  In fact they were normal.

“Now, the murderer must have known of this test.  This clever criminal also knew that to be successful in the use of this drug where others had failed, the drug must be skilfully mixed with something else.  In that first box of capsules there were six.  The druggist compounded them correctly according to the prescription.  But between the time when they came into the house from the druggist’s and the time when she took the first capsule, that night, someone who had access to the house emptied one capsule of its harmless contents and refilled it with a deadly dose of morphine—­a white powder which looks just like the powder already in the capsules.