“What shows the effect?” I interrupted, somewhat impatiently.

“Oh, to be sure,” he smiled.  “I forgot I hadn’t told you what I suspected.  Why, digitalis—­foxglove, you know.  I suppose it never occurred to the police that the rubber dagger might have covered up a peculiar poisoning?  Well, if they’ll take the contents of the stomach, in alcohol, with a little water acidulated, strain off the filtrate and try it on a dog, they will see that its effect is the effect of digitalis.  Digitalis is an accumulative poison and a powerful stimulant of arterial walls, by experimental evidence an ideal drug for the purpose of increasing blood pressure.  Don’t you see it?” he added, excitedly.  “The rubber dagger was only a means to an end.  Some one who knew the weakness of Marchant first placed digitalis in his tea.  That was possible because of the taste of the tea.  Then, in the excitement of the act pantomimed by Errol, Marchant’s disease carried him off, exactly as was to be expected under the circumstances.  It was clever, diabolically clever.  Whoever did it destroyed the note in which the act was suggested and counted that no one would ever stop to search for a poison in the tangle of events.”

Slowly but clearly I began to realize how certainly Kennedy was reconstructing the strange case.  But who was it?  What was the motive back of this sinister murder that had been so carefully planned that no one would ever suspect a crime?

I had hardly framed the queries when our telephone rang.  It was the Central Office man.  The detective had anticipated my own line of inquiry, only had gone much further with it.  He had found a clear record of the business relations existing between Errol and Marchant.  One episode consisted of a stock deal between them in which Errol had invested in a stock which Marchant was promoting and was known to be what brokers call “cats and dogs.”  That, I reasoned, must have been the basis of the gossip that Errol had suffered financial losses that seriously impaired his little fortune.  It was an important item and Kennedy accepted it gladly, but said nothing of his own discovery.  The time had not arrived yet to come out into the open.

For a few moments after the talk with the detective Kennedy seemed to be revolving the case, as though in doubt whether the new information cleared it up or added to the mystery.  Then he rose suddenly.

“We must find Karatoff,” he announced.

Whatever might have been the connection of the hypnotist with this strange case, he was far too clever to betray himself by any such misstep as seeming to avoid inquiry.  We found him easily at his studio apartment, nor did we have any difficulty in gaining admittance.  He knew that he was watched and that frankness was his best weapon of defense.

“Of course,” opened Kennedy, “you know that investigation has shown that you were right in your diagnosis of the trouble with Marchant.  Was it arteriosclerosis for which you were treating him?”