“You think he may have sunk so low as to become a creature of Fu-Manchu?” I asked, aghast.

“Exactly!  If it paid him well I do not doubt that he would serve that master as readily as any other.  His record is about as black as it well could be.  Slattin is of course an assumed name; he was known as Lieutenant Pepley when he belonged to the New York Police, and he was kicked out of the service for complicity in an unsavory Chinatown case.”

“Chinatown!”

“Yes, Petrie, it made me wonder, too; and we must not forget that he is undeniably a clever scoundrel.”

“Shall you keep any appointment which he may suggest?”

“Undoubtedly.  But I shall not wait until tomorrow.”

“What!”

“I propose to pay a little informal visit to Mr. Abel Slattin, to-night.”

“At his office?”

“No; at his private residence.  If, as I more than suspect, his object is to draw us into some trap, he will probably report his favorable progress to his employer to-night!”

“Then we should have followed him!”

Nayland Smith stood up and divested himself of the old shooting-jacket.

“He has been followed, Petrie,” he replied, with one of his rare smiles.  “Two C.I.D. men have been watching the house all night!”

This was entirely characteristic of my friend’s farseeing methods.

“By the way,” I said, “you saw Eltham this morning.  He will soon be convalescent.  Where, in heaven’s name, can he—­”

“Don’t be alarmed on his behalf, Petrie,” interrupted Smith.  “His life is no longer in danger.”

I stared, stupidly.

“No longer in danger!”

“He received, some time yesterday, a letter, written in Chinese, upon Chinese paper, and enclosed in an ordinary business envelope, having a typewritten address and bearing a London postmark.”

“Well?”

“As nearly as I can render the message in English, it reads:  ’Although, because you are a brave man, you would not betray your correspondent in China, he has been discovered.  He was a mandarin, and as I cannot write the name of a traitor, I may not name him.  He was executed four days ago.  I salute you and pray for your speedy recovery.  Fu-Manchu.’”

“Fu-Manchu!  But it is almost certainly a trap.”

“On the contrary, Petrie—­Fu-Manchu would not have written in Chinese unless he were sincere; and, to clear all doubt, I received a cable this morning reporting that the Mandarin Yen-Sun-Yat was assassinated in his own garden, in Nan-Yang, one day last week.”

CHAPTER VIII

DR. FU-MANCHU STRIKES

Together we marched down the slope of the quiet, suburban avenue; to take pause before a small, detached house displaying the hatchet boards of the Estate Agent.  Here we found unkempt laurel bushes and acacias run riot, from which arboreal tangle protruded the notice—­“To be Let or Sold.”