In Lost Valley, the Lost Valley Ranch is a far-reaching empire founded by James Hyland, advanced by his son Angus Hyland, and inherited in the third generation by Douglas Hyland. Sheriff Evan Hatfield is a fair-minded man who wants to maintain the peace. This intention is challenged with the arrival of a homesteader who was issued a claim along Arapaho Creek by the Land Office in Denver. Douglas Hyland has documents in Spanish that support his claims to both sides of Arapaho creek, but he must make a trip to correct the error at the Land Office. New claimants arrive while he is gone and no one is going to stop them from moving onto their claims and building structures — not the aggressive crew of Lost Valley Ranch and certainly not the sheriff.