The Iron Horse - Season 1 Episode 20
The Bridge at Forty-Mile

A man who sold lumber to Calhouns railroad has disappeared, and his brother thus refuses to unload the lumber unless and until he is found to prove the sale was made. Suspecting two renegade Indians who quit just after the man left, Dave sets out to find them, along with the sellers brother. The behaviour of the owner of a trading post leads them to suspect the answers are to be found there.