The Sundown Man — Jory Sherman

When his parents were slaughtered by Arapahos, Jared Sunnedon and his sister Kate made it out alive, only to be taken prisoner. Then and there, they vow that if they are ever separated, they'll never give up the search for each other. After Kate is captured by Utes and sold off, Jared makes good on his promise and escapes. And there's no man alive and no stretch of wasted desert that's going to come between Jared and the only family he's got left.