“All over the world.  We are practically the only source of supply.”

“How do you obtain the serum in quantity?”

“From horses treated with increasing doses of the snake venom.”

A question struck me as I remembered the peculiar double action of the poison.  “Can you tell me just how the antivenin counteracts the effects of the venom?” I inquired of the savant.

“Surely,” he replied.  “It neutralizes one of the two elements in the venom, the nervous poison, thus enabling the individual to devote all his vitality to overcoming the irritant poison.  It is the nervous poison that is the chief death-dealing agent, producing paralysis of the heart and respiration.  We advise all travelers to carry the protective serum if they are likely to be exposed to snake bites.”

Kennedy picked up the tube containing the solution made from the towel spots.  “This antivenin was your product, doctor?”

“Probably so,” was the precise answer.

“Then the purchasers can be identified,” I suggested.

“We have no record of ordinary purchasers,” Nagoya explained, slowly.

Kennedy was keenly disappointed at that, and showed it.  However, he thanked the scientist cordially, and we departed.  Outside, he turned to me.

“Do you understand now why the night intruder at Tarrytown did not die—­if he is one of our suspects—­from the scratch of the needle?”

“You mean he had taken an injection of antivenin before—­”

“Exactly!  We are dealing with a criminal of diabolical cleverness.  Not only did he make all his plans to kill Miss Lamar with the greatest possible care, but he prepared against accident to himself.  He was taking no chances.  He inoculated himself with a protective serum.  The needle of the syringe he used for that purpose he wiped upon the towel you discovered in the washroom.”

XIX

AROUND THE CIRCLE

“I’d like to have another talk with Millard about that Fortune Features affair,” remarked Kennedy.

It was the third morning after the death of Stella Lamar, and I found him half through breakfast when I rose.  About him were piled moving picture and theatrical publications, daily, weekly, and monthly.  At the moment I caught him he had spread wide open the inner page of the Daily Metropolitan, a sheet devoted almost exclusively to sports and the amusement fields.

I went around to glance over his shoulder.  He pointed to a small item under a heading of recent plans and changes.

     Fortune features