“But if Marden’s account is true—­”

“West, as he lost consciousness, saw Marden go in exactly the same way.”

“Marden was seated by the open window, but I cannot conjecture how any one can have got at West, who sat by the table!”

“The case of Marden is little less than remarkable; he was some distance from the window.  No one could possibly have reached him from outside.”

“And the constable?”

“The constable can give us no clue.  He was suddenly struck down, as the others were.  I examined the safe, of course, but didn’t touch it, according to instructions.  Someone had been at work on the lock, but it had defied their efforts.  I’m fully expecting though that they’ll be back to-night, with different tools!”

“The place is watched during the day, of course?”

“Of course.  But it’s unlikely that anything will be attempted in daylight.  Tonight I am going down myself.”

“Could you arrange that I join you?”

“I could, but you can see the danger for yourself?”

“It is extraordinarily mysterious.”

“Mr. Cavanagh, it’s uncanny!” said Bristol.  “I can understand that one of these Hashishin could easily have got up behind the man on duty out in the open.  I know, and so do you, that they’re past masters of that kind of thing; but unless they possess the power to render themselves invisible, it’s not evident how they can have got behind West whilst he sat at the table, with Marden actually watching him!”

“We must lay a trap for them to-night.”

“Rely upon me to do so.  My only fear is that they may anticipate it and change their tactics.  Hassan of Aleppo apparently knows as much of our plans as we do ourselves.”

Inspector Bristol, though a man of considerable culture, clearly was infected with a species of supernatural dread.

CHAPTER VIII

THE VIOLET EYES AGAIN

At four o’clock in the afternoon I had heard nothing further from Bristol, but I did not doubt that he would advise me of his arrangements in good time.  I sought by hard work to forget for a time the extraordinary business of the stolen slipper; but it persistently intruded upon my mind.  Particularly, my thoughts turned to the night of Professor Deeping’s murder, and to the bewitchingly pretty woman who had warned me of the impending tragedy.  She had bound me to secrecy—­a secrecy which had proved irksome, for it had since appeared to me that she must have been an accomplice of Hassan of Aleppo.  At the time I had been at a loss to define her peculiar accent, now it seemed evidently enough to have been Oriental.

I threw down my pen in despair, for work was impossible, went downstairs, and walked out under the arch into Fleet Street.  Quite mechanically I turned to the left, and, still engaged with idle conjectures, strolled along westward.