“That I can believe,” Major Guysburg answered, “if Michaud has to do with it. Mind, he is an extraordinarily clever man. One ramp he was generally supposed eight or ten years ago to have had a hand in concerned the insurance of some valuable stones owned by a diamond merchant whose place of business is in the Kalverstraat in Amsterdam—​I formerly lived near Rotterdam. Within six months after the insurance had been effected the stones disappeared from the merchant’s safe, and to this day nobody knows how the robbery was carried out—​the merchant kept the key of his safe on him day and night. The opinion in Amsterdam, however, was that Michaud, who had insured the stones and who was paid the insurance under protest, was himself the thief. Oh, but there were other queer doings in which he was said to be mixed up, but they would take too long to tell. Incidentally he was supposed at one time to have in his possession a remarkable drug, a sort of perfumed poison, with most peculiar attributes—​it was said that the drug, properly administered, rendered people unconscious, and left their minds a blank after they recovered consciousness, from a period before they inhaled it.”

Preston became greatly interested.

“Tell me, major,” he said, “did you read the report recently of the exhumation of the body of a Jew who died suddenly, and under rather mysterious circumstances, at a ball at the Albert Hall?”

“No. I am not a great newspaper reader.”

“Well, naturally I was interested in the affair because I and a friend of mine found the man dead in one of the boxes during the ball,” and he went on to give Major Guysburg a brief account of what had occurred that night. “Why I am interested in what you say about that peculiar drug is that the man who was believed to know something about the Jew’s death, or rather what caused it, admitted having imported from Shanghai, for his own use only, he said, a drug apparently similar to the one you have just mentioned—​it may, indeed, have been the identical drug.”

“Shanghai, did you say? Why, I remember now that is the place where the drug I have told you about was supposed to have come from.”

“How strange! And there was another affair when apparently some drug of the sort was used, but on that occasion the victim was La Planta himself.”

“La Planta! The name sounds familiar. Now where have I heard that name before?”

He racked his brain for a minute, but in vain.

“La Planta,” Preston said, “was the man believed to know something of the cause of the Jew’s death, but nothing could be proved against him. You may be surprised to hear that La Planta is the younger of the two men constantly with the woman we have just been speaking about, Mrs. Mervyn-Robertson.”