I could not understand it. Had the house been bare of furniture I should have reached the natural conclusion that Kathulos had fled--but no signs of flight met my eye. This was unnatural, uncanny. I stood in the great shadowy library and pondered. No, I had made no mistake in the houses. Even if the broken corpse in the vestibule were not there to furnish mute testimony, everything in the room pointed toward the presence of the Master. There were the artificial palms, the lacquered screen, the tapestries, even the idol, though now no incense smoke rose before it. About the walls were ranged long shelves of books, bound in strange and costly fashion--books in every language in the world, I found from a swift examination, and on every subject--outré and bizarre, most of them. Remembering the secret passage in the Temple of Dreams, I investigated the heavy mahogany table which stood in the center of the room. But nothing resulted. A sudden blaze of fury surged up in me, primitive and unreasoning. I snatched a statuette from the table and dashed it against the shelf-covered wall. The noise of its breaking would surely bring the gang from their hiding-places. But the result was much more startling than that! The statuette struck the edge of a shelf and instantly the whole section of shelves with their load of books swung silently outward, revealing a narrow doorway! As in the other secret door, a row of steps led downward. At another time I would have shuddered at the thought of descending, with the horrors of that other tunnel fresh in my mind, but inflamed as I was by the elixir, I strode forward without an instant's hesitancy. Since there was no one in the house, they must be somewhere in the tunnel or in whatever lair to which the tunnel led. I stepped through the doorway, leaving the door open; the police might find it that way and follow me, though somehow I felt as if mine would be a lone hand from start to grim finish. I went down a considerable distance and then the stair debouched into a level corridor some twenty feet wide--a remarkable thing. In spite of the width, the ceiling was rather low and from it hung small, curiously shaped lamps which flung a dim light. I stalked hurriedly along the corridor like old Death seeking victims, and as I went I noted the work of the thing. The floor was of great broad flags and the walls seemed to be of huge blocks of evenly set stone. This passage was clearly no work of modern days; the slaves of Kathulos never tunneled there. Some secret way of mediæval times, I thought--and after all, who knows what catacombs lie below London, whose secrets are greater and darker than those of Babylon and Rome? On and on I went, and now I knew that I must be far below the earth. The air was dank and heavy, and cold moisture dripped from the stones of walls and ceiling. From time to time I saw smaller passages leading away in the darkness but I determined to keep to the larger main one.