"What! You know this girl! Who is she?"

"She is one of the finest weapons in the enemy's armory, Petrie. But a woman is a two-edged sword, and treacherous. To our great good fortune, she has formed a sudden predilection, characteristically Oriental, for yourself. Oh, you may scoff, but it is evident. She was employed to get this letter placed in my hands. Give it to me."

I did so.

"She has succeeded. Smell."

He held the envelope under my nose, and, with a sudden sense of nausea, I recognized the strange perfume.

"You know what this presaged in Sir Crichton's case? Can you doubt any longer? She did not want you to share my fate, Petrie."

"Smith," I said unsteadily, "I have followed your lead blindly in this horrible business and have not pressed for an explanation, but I must insist before I go one step farther upon knowing what it all means."

"Just a few steps farther," he rejoined; "as far as a cab. We are hardly safe here. Oh, you need not fear shots or knives. The man whose servants are watching us now scorns to employ such clumsy, tell-tale weapons."

Only three cabs were on the rank, and, as we entered the first, something hissed past my ear, missed both Smith and me by a miracle, and, passing over the roof of the taxi, presumably fell in the enclosed garden occupying the center of the square.

"What was that?" I cried.