“May we join you?” she asked.

“By all means,” he returned.  “I was about to suggest it myself.”

We fell in behind with the rest and were off again.

Under the direction of the sailor we came at last to the ravine where we looked about searchingly for some trace of Arnold and Woodward.

“What’s that noise?” exclaimed one of the cavalrymen.

We could hear shots, above us.

“They may need us,” cried Elaine, impatiently.

It was impossible to ride up the sheer height above.

“Dismount,” ordered Captain Price.

His men jumped down and we followed him.  Elaine struggled up, now helped by me, now helping me.

Further down the hill from the deserted house which we could see above us at the top was an underground passage which had been built to divert part of the water above the falls for power.  Through it the water surged and over this boiling stream ran a board walk, the length of the tunnel.

Into this tunnel we could see that a masked man had made his way.  As he did so, he turned for just a moment and fired a volley of shots.

Elaine screamed.  There were Arnold and Woodward, his targets, coming on boldly, as yet unhit.  They rushed in after him, in spite of his running fire, returning his shots and darting toward the tunnel entrance through which he still blazed back at them.

From our end of the ravine, we could see precisely what was going on.  “Come—­the other end of the tunnel,” shouted Price, who had evidently been over the ground and knew it.

We made our way quickly to it and it seemed as if we had our man trapped, like a rat in a hole.

In the tunnel the man was firing back at his pursuers as he ran along the board walk for our end.  He looked up just in time as he approached us.  There he could see Price and his cavalry waiting, cutting off retreat.  We were too many for him.  He turned and took a step back.  There were Arnold and Woodward with levelled guns peering in as though they could not see very clearly.  In a moment their eyes would become accustomed as his to the darkness.  What should he do?  There was not a second to waste.  He looked down at the planks beneath him and the black water slipping past on its way to the power station.  It was a desperate chance.  But it was all that was left.  He dropped down and let himself without even a splash into the water.

Arnold and Woodward took a step into the darkness, scarcely knowing what to expect, their eyes a bit better accustomed to the dusk.  But if they had been there an hour, in all probability they could not have seen what was at their very feet.

Del Mar had sunk and was swimming under water in the swift black current sweeping under them.  As they entered, he passed out, nerved up to desperation.

Down the stream, just before it took its final plunge to the power wheel, Del Mar managed by a superhuman effort to reach out and grasp a wooden support of the flooring again and pull himself out of the stream.  Smiling grimly to himself, he hurried up the bank.