“Karamaneh introduced one in some way.  Do you doubt it?”

“Certainly Karamaneh visited him on the evening of his death, but you must be perfectly well aware that even if she had been arrested, no jury could convict her.”

Smith resumed his restless pacings up and down.

“You are very useful to me, Petrie,” he replied; “as a counsel for the defense you constantly rectify my errors of prejudice.  Yet I am convinced that our presence at Slattin’s house last night prevented Fu-Manchu from finishing off this little matter as he had designed to do.”

“What has given you this idea?”

“Weymouth is responsible.  He has rung me up from the Yard.  The constable on duty at the house where the murder was committed, reports that some one, less than an hour ago, attempted to break in.”

“Break in!”

“Ah! you are interested?  I thought the circumstance illuminating, also!”

“Did the officer see this person?”

“No; he only heard him.  It was some one who endeavored to enter by the bathroom window, which, I am told, may be reached fairly easily by an agile climber.”

“The attempt did not succeed?”

“No; the constable interrupted, but failed to make a capture or even to secure a glimpse of the man.”

We were both silent for some moments; then: 

“What do you propose to do?” I asked.

“We must not let Fu-Manchu’s servants know,” replied Smith, “but to-night I shall conceal myself in Slattin’s house and remain there for a week or a day—­it matters not how long—­until that attempt is repeated.  Quite obviously, Petrie, we have overlooked something which implicates the murderer with the murder!  In short, either by accident, by reason of our superior vigilance, or by the clumsiness of his plans, Fu-Manchu for once in an otherwise blameless career, has left a clue!”

CHAPTER X

THE CLIMBER RETURNS

In utter darkness we groped our way through into the hallway of Slattin’s house, having entered, stealthily, from the rear; for Smith had selected the study as a suitable base of operations.  We reached it without mishap, and presently I found myself seated in the very chair which Karamaneh had occupied; my companion took up a post just within the widely opened door.

So we commenced our ghostly business in the house of the murdered man —­a house from which, but a few hours since, his body had been removed.  This was such a vigil as I had endured once before, when, with Nayland Smith and another, I had waited for the coming of one of Fu-Manchu’s death agents.

Of all the sounds which, one by one, now began to detach themselves from the silence, there was a particular sound, homely enough at another time, which spoke to me more dreadfully than the rest.  It was the ticking of the clock upon the mantelpiece; and I thought how this sound must have been familiar to Abel Slattin, how it must have formed part and parcel of his life, as it were, and how it went on now—­tick-tick-tick-tick—­whilst he, for whom it had ticked, lay unheeding—­ would never heed it more.