“Not a blessed thing,” returned the coroner.  “I’m desperate.  One of the chemists suggested cyanide, another carbon monoxide.  But there is no trace of either.  Then he suggested nux vomica.  It wasn’t nux vomica; but my tests show that it must have been something very much like it.  I’ve looked for all the ordinary known poisons and some of the little-known alkaloids, but, Kennedy, I always get back to the same point.  There must have been a poison there.  He did not die primarily of the wound.  It was asphyxia due to a poison that really killed him, though the wound might have done so, but not quite so quickly.”

I could tell by the look that crossed Kennedy’s face that at last a ray of light had pierced the darkness.  He reached for a bottle on the shelf labelled spirits of turpentine.

Then he poured a little of the blood sample from the jar which the coroner had brought into a clean tube and added a few drops of the spirits of turpentine.  A cloudy, dark precipitate formed.  He smiled quietly, and said, half to himself, “I thought so.”

“What is it?” asked the coroner eagerly, “nux vomica?”

Craig shook his head as he stared at the black precipitate.  “You were perfectly right about the asphyxiation, Doctor,” he remarked slowly, “but wrong as to the cause.  It was a poison—­one you would never dream of.”

“What is it?” Leslie and I asked simultaneously.

“Let me take all these samples and make some further tests,” he said.  “I am quite sure of it, but it is new to me.  By the way, may I trouble you and Leslie to go over to the Museum of Natural History with a letter?”

It was evident that he wanted to work uninterrupted, and we agreed readily, especially because by going we might also be of some use in solving the mystery of the poison.

He sat down and wrote a hasty note to the director of the Museum, and a few moments later we were speeding over in Leslie’s car.

At the big building we had no trouble in finding the director and presenting the note.  He was a close friend of Kennedy’s and more than willing to aid him in any way.

“You will excuse me a moment?” he apologized.  “I will get from the South American exhibit just what he wants.”

We waited several minutes in the office until finally he returned carrying a gourd, incrusted on its hollow inside surface with a kind of blackish substance.

“That is what he wants, I think,” the director remarked, wrapping it up carefully in a box.  “I don’t need to ask you to tell Professor Kennedy to watch out how he handles the thing.  He understands all about it.”

We thanked the director and hurried out into the car again, carrying the package, after his warning, as though it were so much dynamite.

Altogether, I don’t suppose that we could have been gone more than an hour.

We burst into the laboratory, but, to my surprise, I did not see Kennedy at his table.  I stopped short and looked around.