Together we ran to the trap and looked down.

Slowly moving tidal water flowed darkly beneath us!  For twenty breathless seconds we watched—­but nothing showed upon the surface.

“I hope his swimming is no better than his shooting,” I said.

“It can avail him little,” replied Harley grimly; “a river-police boat is waiting for anyone who tries to escape from that side of the house.  We are by no means alone in this affair, Knox.  But, firstly, what have we here!” He took up the bundle which the fugitive had deserted.  “Something incriminating when Ali of Cairo dared not stay to face it out!  He would never have deserted this place in the ordinary way.  That fellow who was such a bad shot was left behind, when the news of our approach reached here, to make a desperate attempt to remove some piece of evidence!  I’ll swear to it.  But we were too soon for him!”

All the time he was busily removing the pieces of sacking and scraps of Oriental stuff with which the bundle was fastened; and finally he drew out a dress-suit, together with the linen, collar, shoes, and underwear—­a complete outfit, in fact—­and on top of the whole was a soft gray felt hat!

Eagerly Harley searched the garments for some name of a maker by which their owner might be identified.  Presently, inside the lining of the breast pocket, where such a mark is usually found, he discovered the label of a well-known West End firm.

“The police can confirm it, Knox!” he said, looking up, his face slightly flushed with triumph; “but I, personally, have no doubt!”

“You may have no doubt, Harley,” I retorted, “but I am full of doubt!  What is the significance of this discovery to which you seem to attach so much importance?”

“At the moment,” replied my friend, “never mind; I still have hopes—­although they have grown somewhat slender—­of making a much more important discovery.”

“Why not permit the police to aid in the search?”

“The police are more useful in their present occupation,” he replied.  “We are dealing with the most cunning knave produced by East or West, and I don’t mean to let him slip through my fingers if he is in this house!  Nevertheless, Knox, I am submitting you to rather an appalling risk, I know; for our man is desperate, and if he is still in the place will prove as dangerous as a cornered rat.”

“But the man who dropped through the trap?”

“The man who dropped through the trap,” said Harley, “was not Ali of Cairo—­and it is Ali of Cairo for whom I am looking!”

“The hunchback we saw to-night?”

Harley nodded, and having listened intently for a few moments, proceeded again to search the singular apartments of the abode.  In each was evidence of Oriental occupancy; indeed, some of the rooms possessed a sort of Arabian Nights atmosphere.  But no living creature was to be seen or heard anywhere.  It was while the two of us, having examined every inch of wall, I should think, in the building, were standing staring rather blankly at each other in the room with the lighted lantern, that I saw Harley’s expression change.