Again it was his impulse to go, and again he stayed.

There was a slight gurgling in the water almost at his feet, and a dark figure rose from the waves, followed in an instant by another, and then by many more.
Robert, his imagination up and leaping, thrilled with horror.

He understood at once.

They were attacked by swimming savages.

While the great shouting and turmoil in their front was going on a line of warriors had reached the lake somewhere in the darkness, and were now in the camp itself.
He was palsied only for a moment.