"That pigtail!" he cried. "I have left it behind! We must have it, Petrie! Stop! Stop!"

The cab was pulled up, and Smith alighted.

"Don't wait for me," he directed hurriedly. "Here, take Weymouth's card. Remember where he said the book was? It's all we want. Come straight on to Scotland Yard and meet me there."

"But Smith," I protested, "a few minutes can make no difference!"

"Can't it!" he snapped. "Do you suppose Fu-Manchu is going to leave evidence like that lying about? It's a thousand to one he has it already, but there is just a bare chance."

It was a new aspect of the situation and one that afforded no room for comment; and so lost in thought did I become that the cab was outside the house for which I was bound ere I realized that we had quitted the purlieus of Wapping. Yet I had had leisure to review the whole troop of events which had crowded my life since the return of Nayland Smith from Burma. Mentally, I had looked again upon the dead Sir Crichton Davey, and with Smith had waited in the dark for the dreadful thing that had killed him. Now, with those remorseless memories jostling in my mind, I was entering the house of Fu-Manchu's last victim, and the shadow of that giant evil seemed to be upon it like a palpable cloud.

Cadby's old landlady greeted me with a queer mixture of fear and embarrassment in her manner.

"I am Dr. Petrie," I said, "and I regret that I bring bad news respecting Mr. Cadby."

"Oh, sir!" she cried. "Don't tell me that anything has happened to him!" And divining something of the mission on which I was come, for such sad duty often falls to the lot of the medical man: "Oh, the poor, brave lad!"

Indeed, I respected the dead man's memory more than ever from that hour, since the sorrow of the worthy old soul was quite pathetic, and spoke eloquently for the unhappy cause of it.