“The next day I managed, as I have said, to go over the room thoroughly with a vacuum cleaner—­a new one of my own which I had bought myself.  But tests of the dust which I got from the floors, curtains, and furniture showed nothing at all.  As a last thought I had, however, cleaned the mattress of the bed and the cracks and crevices in the brass bars.  Teats of that dust showed it to be extremely radioactive.  I had the dust dissolved, by a chemist who understands that sort of thing, recrystallized, and the radium salts were extracted from the refuse.  Thus I found that I had recovered all but a very few milligrams of the radium that had been originally purchased in London.  Here it is in this deadly tube in the leaden casket.

“It is needless to add that the night after I had cleaned out this deadly element the maid slept the sleep of the just—­and would have been all right when next I saw her but for the interference of the unjust on whom I had stolen a march.”

Craig paused while the lawyers whispered again to their clients.  Then he continued:  “Now three persons in this room had an opportunity to secrete the contents of this deadly tube in the crevices of the metal work of Mrs. Close’s bed.  One of these persons must have placed an order through a confidential agent in London to purchase the radium from the English Radium Corporation.  One of these persons had a compelling motive, something to gain by using this deadly element.

“The radium in this tube in the casket was secreted, as I have said, in the metal work of Mrs. Close’s bed, not in large enough quantities to be immediately fatal, but mixed with dust so as to produce the result more slowly but no less surely, and thus avoid suspicion.  At the same time Mrs. Close was persuaded—­I will not say by whom—­through her natural pride, to take a course of X-ray treatment for a slight defect.  That would further serve to divert suspicion.  The fact is that a more horrible plot could hardly have been planned or executed.  This person sought to ruin her beauty to gain a most selfish and despicable end.”

Again Craig paused to let his words sink into our minds.

“Now I wish to state that anything you gentlemen may say will be used against you.  That is why I have asked you to bring your attorneys.  You may consult with them, of course, while I am getting ready my next disclosure.”

As Kennedy had developed his points in the case I had been more and more amazed.  But I had not failed to notice how keenly Lawrence was following him.

With half a sneer on his astute face, Lawrence drawled:  “I cannot see that you have accomplished anything by this rather extraordinary summoning of us to your laboratory.  The evidence is just as black against Dr. Gregory as before.  You may think you’re clever, Kennedy, but on the very statement of facts as you have brought them out there is plenty of circumstantial evidence against Gregory—­more than there