It's the ghost of Whistlin' Dan." The tall roan raised his head and whinnied softly.

It was an unearthly effect--as if the animal heard the sound which was inaudible to all but his master.

It changed big Jim Silent into a quavering coward.
Here were five practised fighters who feared nothing between heaven and hell, but what could they avail him against a bodiless spirit?
The whistling stopped.

He breathed again, but only for a moment.
It began again, and this time much louder and nearer.

Surely the others must hear it now, or else it was certainly a ghost.