The shadow had disappeared behind a tree.

He fixed his keen eyes on that tree and presently a dark object glided from it and darted stealthily forward to another tree.

One, two, three dark forms followed the first one.

They were Indian warriors, and they moved so quickly that only the eyes of a woodsman like Wetzel could have discerned their movements at that distance.
Probably most hunters would have taken to their heels while there was yet time.

The thought did not occur to Wetzel.