We followed some of them for a distance, but found none that gave any particular promise.  Most of them were choked with rocks and boulders through which it was difficult to force a passage.  We spent an hour or more in these futile explorations, then followed the wall some distance to the right.

Gradually the exits became less numerous.  High on a boulder near the entrance of one we saw the head of some animal peering down at us.  We hurled our spears at it, but missed; then were forced to climb up the steep side of the boulder to recover our weapons.

“We’d better go back to Desiree,” said Harry when we reached the ground again.  “She’ll wonder what’s become of us.  We’ve been gone nearly two hours.”

After fifteen minutes’ search we found the stream, and followed it to the left.  We had gone farther than we thought, and we were looking for the end, where we had left Desiree, long before we reached it.  Several times we called her name, but there was no answer.

“She’s probably asleep,” said Harry.  And a minute later:  “There’s the wall at last!  But where is she?”

My foot struck something on the ground, and I stooped over to examine it.

It was the pile of skins on which Desiree had lain!

I called to Harry, and at the same instant heard his shout of consternation as he came running toward me, holding something in his hand.

“They’ve got her!  Look!  Look at this!  I found it on the ground over there.”

He held the thing in his hand out before me.

It was an Inca spear.

Chapter XXI.

The midst of the enemy.

Harry and I stood gazing at each other blankly in the semidarkness of the cavern.

“But it isn’t possible,” I objected finally to my own thoughts.  “She would have cried out and we would have heard her.  The spear may have been there before.”

Then I raised my voice, calling her name many times at the top of my lungs.  There was no answer.

“They’ve got her,” said Harry, “and that’s all there is to it.  The cursed brutes crept up on her in the dark—­much chance she had of crying out when they got their hands on her.  I know it.  Why did we leave her?”

“Where did you find the spear?” I asked.

Harry pointed toward the wall, away from the stream.

“On the ground?”

“Yes.”

“Is there an exit from the cavern on that side?”

“I don’t know.”

“Well, that’s our only chance.  Come on!”

We found the exit, and another, and a third.  Which to take?  They were very similar to one another, except that the one in the middle sloped upward at a gentle incline, while the others were level.

“One is as good as another,” I observed, and entered the one on the left.

Once started, we advanced with a rush.  The passage was straight and narrow, clear of obstruction, and we kept at a steady run.