Suddenly it crouched lower still against the black background of the boulder.

“Another second and he will be at my throat,” I thought—­but I stood still, unable to move.

But the figure did not spring.  Instead, it suddenly straightened up to almost twice the height of an Inca, and I caught a glimpse of a white face and ragged, clinging garments.

“Harry!” I whispered.  I wonder yet that it was not a shout.

“Thank God!” came his voice, also in a whisper; and in another moment he had reached my side.

A hurried word or two—­there was no time for more—­and I pointed to the Incas on the raft, saying:  “We want those spears.”

“I was after them,” he grinned.  “What shall we do?”

“There’s no use taking them while the Incas are away,” I replied, “because they would soon return and find them gone.  Surely we can handle two of them.”

As I spoke there came a sound from the lake—­a sudden loud splash followed by a commotion in the water.  I looked around the corner of the boulder and saw that the spears again found their mark.

“Come,” I whispered, and began to pick my way toward the ledge.

Harry followed close at my heels.  It was easier here, and we soon found ourselves close to the shore of the lake, with a smooth stretch of rock between us and the fisherman’s landing-place.  The urns, whose light was quite sufficient here, were about fifty feet to the right and rear.

The Incas had made their kill and were paddling for the shore.  As they came near, Harry and I sank back against the boulder, which extended to the boundary of the ledge.  Soon the raft was beached and pulled well away from the water, and the fish—­I was amazed at its size—­followed.

They drew forth the spears and laid them on the ground, as they had done formerly; and, laying hold on the immense fish, still floundering ponderously about, began to drag it toward the mouth of the passage.

“Now,” whispered Harry, and as he stood close at my side I could feel his body draw together for the spring.

I laid a hand on his arm.

“Not yet.  Others may be waiting for them in the passage.  Wait till they return.”

In a few minutes they reappeared in the light of the flaming urns.  I waited till they had advanced half-way to the water’s edge, some thirty feet away.  Then I whispered to Harry:  “You for the left, me for the right,” and released my hold on his arm, and the next instant we were bounding furiously across the ledge.

Taken by surprise, the Incas offered no resistance whatever.  The momentum of our assault carried them to the ground; their heads struck the hard granite with fearful force and they lay stunned.

Harry, kneeling over them, looked up at me with a question in his eyes.

“The lake,” said I, for it was no time for squeamishness.

Our friend the king thought us dead, and we wanted no witnesses that we had returned to life.  We laid hold of the unconscious bodies, dragged them to the edge of the lake, and pushed them in.  The shock of the cold water brought one of them to life, and he started to swim, and we—­well, we did what had to be done.