The situation was becoming clearer and clearer. There was no need for me to ask the specialist where he had procured the contents of the glass bottle. I could see what must have happened. The explorer’s narrative must have contained some account of an unknown poison peculiar to the Island of Sumatra; the expert’s attention had been drawn to it; he had approached the author, found that he had some of the poison in his possession, and induced him to part with it. His object now must be to find out whether Armstrong had kept any himself, or allowed it to get into other hands.

I was so relieved at the turn the investigation was taking that I had ceased to worry about my own connection with the tragedy. It gave me a disagreeable shock to be reminded that there were other points to be cleared up, when my chief spoke again.

“I think our next step now must be to interview Sarah Neobard. I doubt if she has told us all she knows about Weathered and his woman patients. She may be able to throw some light on the mysterious numbers.”

The numbers in the appointment-book were as mysterious to me as they were to him. I had been able to form no theory as to their significance; nevertheless, I felt that danger lay in that direction. I could not forget that a number had been attached to Violet Bredwardine’s name, and I dreaded to learn why.

The physician was provided with a good excuse for presenting himself again at the house in Warwick Street. It was necessary to make arrangements for the interment of the body. He had decided, he told me, to give a certificate that would dispense with the necessity for an inquest, and permit of the funeral taking place without delay. For that purpose the body was to be conveyed to the house in the small hours when nobody was likely to be about.

It was a strong thing to do before it had yet been determined whether the murder was to be made the subject of a public prosecution, and the murderer brought to justice. So far as I could see, the authorities both of the Home Office and the Foreign Office were placing entire confidence in my chief, and had given him a free hand. I hoped accordingly that his decision to let the funeral proceed quietly meant that he had made up his mind against any public exposure. But on that point he had been careful not to commit himself, and I was afraid to show too much curiosity.

He took me round with him in the car to Warwick Street, and asked to see Mrs. Weathered. The youthful butler eyed us with the utmost apprehension, and showed us into the patients’ waiting-room. There we were joined presently by the widow and her daughter.

Mrs. Weathered was in deep black. Her manner showed that she was resigned to her husband’s fate by this time, but she was evidently in a state of extreme nervousness, as she well might be while the mystery was unsolved. Sarah, on the other hand, at the beginning of the interview, was as cold and self-possessed as though her part was over, and she had ceased to feel any personal interest in the sequel.

“I have called on you,” Tarleton explained, “to let you know officially that I have examined into the cause of Dr. Weathered’s death, and am prepared to certify that it was due to heart failure.”

I stared. In one sense, of course, almost every death may be said to be due to heart failure. The question generally is what has caused the heart to fail; and I knew perfectly well that the burial certificate would have to be more explicit. But Mrs. Weathered showed herself quite satisfied.