“The humidity; that’s easily understood.  But you’ll have to put up with it in the future.  After nightfall our windows must be closed entirely, Smith.”

Nayland Smith knocked out his pipe upon the side of the fireplace.  The bowl sizzled furiously, but without delay he stuffed broad-cut mixture into the hot pipe, dropping a liberal quantity upon the carpet during the process.  He raised his eyes to me, and his face was very grim.

“Petrie,” he said, striking a match on the heel of his slipper, “the resources of Dr. Fu-Manchu are by no means exhausted.  Before we quit this room it is up to us to come to a decision upon a certain point.”  He got his pipe well alight.  “What kind of thing, what unnatural, distorted creature, laid hands upon my throat to-night?  I owe my life, primarily, to you, old man, but, secondarily, to the fact that I was awakened, just before the attack—­by the creature’s coughing—­by its vile, high-pitched coughing . . .”

I glanced around at the books upon my shelves.  Often enough, following some outrage by the brilliant Chinese doctor whose genius was directed to the discovery of new and unique death agents, we had obtained a clue in those works of a scientific nature which bulk largely in the library of a medical man.  There are creatures, there are drugs, which, ordinarily innocuous, may be so employed as to become inimical to human life; and in the distorting of nature, in the disturbing of balances and the diverting of beneficent forces into strange and dangerous channels, Dr. Fu-Manchu excelled.  I had known him to enlarge, by artificial culture, a minute species of fungus so as to render it a powerful agent capable of attacking man; his knowledge of venomous insects has probably never been paralleled in the history of the world; whilst, in the sphere of pure toxicology, he had, and has, no rival; the Borgias were children by comparison.  But, look where I would, think how I might, no adequate explanation of this latest outrage seemed possible along normal lines.

“There’s the clue,” said Nayland Smith, pointing to a little ash-tray upon the table near by.  “Follow it if you can.”

But I could not.

“As I have explained,” continued my friend, “I was awakened by a sound of coughing; then came a death grip on my throat, and instinctively my hands shot out in search of my attacker.  I could not reach him; my hands came in contact with nothing palpable.  Therefore I clutched at the fingers which were dug into my windpipe, and found them to be small—­as the marks show—­and hairy.  I managed to give that first cry for help, then with all my strength I tried to unfasten the grip that was throttling the life out of me.  At last I contrived to move one of the hands, and I called out again, though not so loudly.  Then both the hands were back again; I was weakening; but I clawed like a madman at the thin, hairy arms of the strangling thing, and with a blood-red mist dancing before my eyes, I seemed to be whirling madly round and round until all became a blank.  Evidently I used my nails pretty freely—­and there’s the trophy.”