I tried to reason it out as we walked along in silence.  Marchant had known Edith Gaines intimately.  Carita Belleville had known Errol as well.  I recalled Errol hovering about Mrs. Gaines at the tea and the incident during the seance when Carita Belleville had betrayed her annoyance over some remark by Errol.  The dancing by Edith Gaines had given a flash of the jealous nature of the woman.  Had it been interest in Errol that had led her to visit the laboratory?  Kennedy was weaving a web about some one, I knew.  But about whom?

As we passed a corner, he paused, entered a drugstore and called up several numbers at a pay-station telephone booth.  Then we turned into the campus and proceeded rapidly toward the laboratory of the psychological department.  Gaines was there, sitting at his desk, writing, as we entered.

“I’m glad to see you,” he greeted, laying down his work.  “I am just finishing the draft of my report on that Karatoff affair.  I have been trying to reach you by telephone to know whether you would add anything to it.  Is there anything new?”

“Yes,” returned Kennedy, “there is something new.  I’ve just come from Karatoff’s and on the way I decided suddenly that it was time we did something.  So I have called up, and the police will bring Errol here, as well as Miss Belleville.  Karatoff will come—­he won’t dare stay away; and I also took the liberty of calling Mrs. Gaines.”

“To come here?” repeated Gaines, in mild surprise.  “All of them?”

“Yes.  I hope you will pardon me for intruding, but I want to borrow some of your psychological laboratory apparatus, and I thought the easiest way would be to use it here rather than take it all over to my place and set it up again.”

“I’m sure everything is at your service,” offered Gaines.  “It’s a little unexpected, but if the others can stand the chaotic condition of the room, I guess we can.”

Kennedy had been running his eye over the various instruments which Gaines and his students used in their studies, and was now examining something in a corner on a little table.  It was a peculiar affair, quite simple, but conveying to me no idea of its use.  There seemed to be a cuff, a glass chamber full of water into which it fitted, tubes and wires that attached various dials and recording instruments to the chamber, and what looked like a chronograph.

“That is my new plethysmograph,” remarked Gaines, noting with some satisfaction how Kennedy had singled it out.

“I’ve heard the students talk of it,” returned Kennedy.  “It’s an improved apparatus, Walter, that records one’s blood flow.”  I nodded politely and concealed my ignorance in a discreet silence, hoping that Gaines would voluntarily enlighten us.

“One of my students is preparing an exhaustive table,” went on Gaines, as I had hoped, “showing the effects on blood distribution of different stimuli—­for instance, cold, heat, chloroform, arenalin, desire, disgust, fear; physical conditions, drugs, emotions—­all sorts of things can be studied by this plethysmograph which can be set to record blood flow through the brain, the extremities, any part of the body.  When the thing is charted I think we shall have opened up a new field.”