We sought the royal apartments.  Those we knew to be on a level some forty or fifty feet below the surface of the great cavern, at the foot of the flight of steps which led to the tunnel to the base of the column.  I had counted ninety-six of those steps, and allowing an average height of six inches, they represented a distance of forty-eight feet.

How far the whirlpool and the stream which it fed had carried us downward we did not know, but we estimated it at one hundred feet.  That calculation left us still fifty feet below the level of the royal apartments.

But we soon found that in this we were mistaken.  We had advanced for perhaps a quarter of an hour without incident when the passage came to an abrupt end.  To the right was an irregular, twisting lane that disappeared around a corner almost before it started; to the left a wide and straight passage, sloping gently upward.  We took the latter.

We had followed this for about a hundred yards when we saw a light ahead.  Caution was useless; the passage was straight and unbroken and only luck could save us from discovery.  We pushed on, and soon stood directly within the light which came from an apartment adjoining the passage.  It was not that which we sought, however, and we gave it barely a glance before we turned to the right down a cross passage, finding ourselves again in darkness.

Soon another light appeared.  We approached.  It came from a doorway leading into an apartment some twenty feet square.  It was empty, and we entered.

There were two flaming urns fastened to the wall above a granite couch.  Stone seats were placed here and there about the room.  The walls were studded with spots of gold to a height of four or five feet.

We stopped short, gazing about us.

“It looks like—­” Harry whispered, and then exclaimed:  “It is!  See, here is where we took the blocks from this seat!”

So it was.  We were in the room where we had imprisoned the Inca king and where we ourselves had been imprisoned with Desiree.

“She said her room was to the right of this,” whispered Harry excitedly.  “What luck!  If only—­”

He left the sentence unfinished, but I understood his fear.  And with me there was even no doubt; I had little hope of finding Desiree, and was sorry, for Harry’s sake, that we had been so far successful.

Again we sought the passage.  A little farther on it was crossed by another, running at right angles in both directions.  But to the right there was nothing but darkness, and we turned to the left, where, some distance ahead, we could see a light evidently proceeding from a doorway similar to the one we had just left.

We went rapidly, but our feet made scarcely any sound on the granite floor.  Still we were incautious, and it was purely by luck that I glanced ahead and discovered that which made me jerk Harry violently back and flatten myself against the wall.