The Saga of Harlan Waugh (The Mountain Men Book #6)
Harlan Waugh is a lone Mountain Man. He hunts in the Rocky Mountains of the early 1830s. Two Crow Indian boys in need of a family cross his path, and Harlan adopts them and teaches them the ways of beaver trapping and buffalo hunting. In their travels, they befall one cruelty after another, until the Mountain Man can't stand it anymore.
If Harlan takes a liking to your miserable carcass, he is a friend for life. But break the unwritten laws of the Western Frontier or the principles of humanity, he will hunt you down as ruthlessly as only a Mountain Man can.
In a lawless land, justice must come from the hands of a tireless vigilante such as this.