He saw a tall fern waver and tremble.

A rabbit, or perhaps a snake, had brushed it.

Other ferns moved, their tops agitated, perhaps, by a faint breeze.

No; that wavering line came straight toward him; it could not be the wind; it marked the course of a creeping, noiseless thing.

It must be a panther crawling nearer and nearer.
Joe opened his lips to awaken his captors, but could not speak; it was as if his heart had stopped beating.