Searching for brother and nephew or gold?

The premise of the movie was that a guy was searching for his brother and nephew who went missing during a trapping trip.

So was this only a ploy to get a guide to lead them to gold? How did they know that the gold was there?

Was there ever a lost brother and nephew? Some body please explain because I didn't understand this film. I did enjoy looking at the attractive Lenore as Dr. Sarah.