There was a heavy crashing in the undergrowth and a deer, wild with alarm, darting within a dozen feet of Dick, disappeared in the forest, running madly.
He knew there were many deer in the Mississippi woods, but he was observant and the flight aroused his attention.

His first thought that he and his horse had scared the deer could not be true, because it had come from a point directly behind and had rushed past them.

Then its alarm must have been caused by some other human being near by in the forest or by a panther.

His theory inclined to the human being.
Dick was troubled.

The more he thought of the incident the less he liked it.