“Were you acquainted with a Captain Shirley?” he asked, finally, as she opened the way for the question by a remark about her life in Calcutta.

“Y-yes,” she replied, hesitating; “I read in the papers this morning that he was found dead, most mysteriously.  Terrible, wasn’t it?  Yes, I met him in Calcutta while I was there.  Why, he was on his way to London, and came to New York and called on me.”

My eye followed the direction of Mrs. Rogers’s.  She was talking to us, but really her attention was centered on Mrs. Anthony and the swami together.  As I glanced back at her I caught sight of Singh, evidently engaged in watching the same two that I was.  Did he have some suspicion of Mrs. Anthony?  Why was he watching Mrs. Rogers?  I determined to study the two women more closely.  I saw that Kennedy had already noticed what I had seen.

“One very peculiar thing,” he said, deliberately modulating his voice so that it could be heard by those about us, “was that, just before he was killed, some one sent a prayer-bean from a necklace to him.”

At the mention of the necklace I saw that Mrs. Rogers was all attention.  Involuntarily she shot a glance at Mrs. Anthony, as if she noted that she was not wearing the necklace now.

“Is that Englishwoman a member of the cult?” queried Kennedy, a moment later, as, quite naturally, he looked over at Mrs. Anthony.  “Who is she?”

“Oh,” replied Mrs. Rogers, quickly, “she isn’t an Englishwoman at all.  She is a Hindu—­I believe, a former nautch-girl, daughter of a nautch-girl.  She passes by the name of Mrs. Anthony, but really her name is Kalia Dass.  Every one in Calcutta knew her.”

Kennedy quietly drew his card-case from his pocket and handed a card to Mrs. Rogers.

“I should like to talk to you about her some time,” he said, in a careful whisper.  “If anything happens—­don’t hesitate to call on me.”

Before Mrs. Rogers could recover from her surprise Kennedy had said good-by and we were on our way to the laboratory.

“That’s a curious situation,” I observed.  “Can you make it out?  How does Shirley fit into this thing?”

Craig hesitated a moment, as though debating whether to say anything, even to me, about his suspicions.

“Suppose,” he said, slowly, “that Shirley was a secret agent of the British government, charged with the mission of finding out whether Mrs. Rogers was contributing—­unknowingly, perhaps—­to hatching another Indian mutiny?  Would that suggest anything to you?”

“And the nautch-girl whom he had known in Calcutta followed him, hoping to worm from him the secrets which he—­”

“Not too fast,” he cautioned.  “Let us merely suppose that Shirley was a spy.  If I am not mistaken, we shall see something happen soon, as a result of what I said to Mrs. Rogers.”

Excited now by the possibilities opened up by his conjecture regarding Shirley, which I knew must have amounted to a certainty in his mind, I watched him impatiently, as he calmly set to work cleaning up the remainder of the laboratory investigation in the affair.