“Then my contention collapses and she was not poisoned?”

“No, I do not say that.  All I say is that expert testimony would refute us as far as we have gone.  But if you will let me make a few tests of my own I can readily clear up that end of the case, I now feel sure.  Let me take these samples to my laboratory.”

I was surprised when we ran into Inspector O’Connor waiting for us in the corridor of the Criminal Courts Building as we left the office of the coroner’s physician.  He rushed up to Kennedy and shoved into his hand a pill-box in which six capsules rattled.  Kennedy narrowly inspected the box, opened it, and looked thoughtfully at the six white capsules lying so innocently within.

“One of these capsules would have been worth hundreds of thousands of dollars to ‘John,’” said Craig contemplatively, as he shut the box and deposited it carefully in his inside vest pocket.  “I don’t believe I even said good morning to you, O’Connor,” he continued.  “I hope I haven’t kept you waiting here long.  Have you obtained the samples of ink?”

“Yes, Professor.  Here they are.  As soon as you telephoned this morning I sent my men out separately to get them.  There’s the ink from the druggist, this is from the Vandam library, this is from Farrington’s room, and this is from Mrs. Popper’s apartment.”

“Thank you, Inspector.  I don’t know what I’d do without your help,” said Kennedy, eagerly taking four small vials from him.  “Science is all right, but organisation enables science to work quickly.  And quickness is the essence of this case.”

During the afternoon Kennedy was very busy in his laboratory, where I found him that night after my hurried dinner, from which he was absent.

“What, is it after dinner-time?” he exclaimed, holding up a glass beaker and watching the reaction of something he poured into it from a test-tube.

“Craig, I believe that when you are absorbed in a case, you would rather work than eat.  Did you have any lunch after I left you?”

“I don’t think so,” he replied, regarding the beaker and not his answer.  “Now, Walter, old fellow, I don’t want you to be offended with me, but really I can work better if you don’t constantly remind me of such things as eating and sleeping.  Say, do you want to help me—­really?”

“Certainly.  I am as interested in the case as you are, but I can’t make heads or tails of it,” I replied.

“Then, I wish you would look up Mrs. Popper to-night and have a private seance with her.  What I want you to do particularly is to get a good idea of the looks of the room in which she is accustomed to work.  I’m going to duplicate it here in my laboratory as nearly as possible.  Then I want you to arrange with her for a private ‘circle’ here to-morrow night.  Tell her it is with a few professors at the university who are interested in psychical research and that Mr. Vandam will be present.  I’d rather have her come willingly than to force her to come.  Incidentally watch that manager of hers, Farrington.  By all means he must accompany her.”