"Things are distinctly looking up," he said. "Thanks to our rather inept attempted murderer, there are now a vast number of new leads in this rather chaotic tangle. It now becomes a rather intriguing project to see where they will take us."

"You have a theory?" I fished. "Who are those men, and why should they want to murder this lady now, when they had her a prisoner for so long totally at their mercy?"

"Bravo, Watson," said the detective. "You have put your finger upon the primary missing link in our chain: motivation. It is not very difficult now to reconstruct what has happened. We even know why it was done. I am now concerned with finding the why behind the why, as it were."

"Why the murder was attempted?" I asked, feeling very slow.

"That puzzled me at first, I confess. It was not of a piece with the rest. Yet I think I can account for it. I am convinced it hinges upon this lady's remarkable memory. You do not see it? Let me recapitulate what we now know.

"This lady has been kept a prisoner, drugged and helpless, for several weeks by two men, antecedents unknown. The one we have now seen upon our stage, the one who calls himself Ormond Sacker, has not cut a very impressive figure. I believe, however, that among that farrago of lies he told Lestrade he inadvertently let fall one true fact; his companion is a medical man. In truth, I've been waiting for someone with such a background to turn up in the case ever since we observed those spots upon the lady's scalp. This doctor is obviously the leader of the two, the dominant personality, and the engineer of our lady's amnesia. Why?

"I theorize she was a witness, Watson, of a most unique sort. A witness whose eidetic memory would be unconfused by time, the pressure of suggestion, or the distortions of emotion. A witness whose memory of minute detail would make her a powerful threat to the most subtle plot or activity, one so camouflaged as to pass invisibly before the ordinary observer.