He could not see the man who had shot the burros.

By the intervals between shots, Casey guessed that one man was doing the shooting, though it was probable there were others in the gang.

And now that the burros were dead, it became more than ever necessary to locate the gang and have it out with them.

That necessity did not worry Casey in the least.

The only thing that troubled him now was getting up on the rim without being seen.
It was characteristic of Casey Ryan that, though he moved with caution, he nevertheless moved toward their unseen enemy.