The Cartwrights try to disprove the validity of a Spanish land grant to stop the De La Cuesta family from seizing part of the Ponderosa and all of the Carson Valley settlers' homestead lands. 

As is often the case on Bonanza, things are not always as they first seem. Hoss and Adam eventually learn who is the good guy and who is not. When a brutal U.S. Marshal arrests one of the Ponderosa's workers for murder to transport him to Los Angeles for trial, and a doubtful Hoss and Adam come along in the stagecoach, along with a Dr. and his beautiful daughter, to make sure the Marshal doesn't kill him before they get there. The question also arises later of whether the ranch worker is really guilty and dangerous after all.