Hoppy and Red arrest a young man whom they find wounded near the body of his uncle, but they soon learn that he's suffering from amnesia and try to clear him.
Assigned to guard the workers building Arizona's first telegraph line, Hoppy learns that a supposedly retired man who owns several stores will lose a fortune if the line is completed, and uses wiretapping to foil a sabotage scheme.
Hoppy and Red discover that two outlaws have ambushed the sheriff of Stone Valley and determine to help the local ranchers against an exploiter who wants to take over the valley and sell it ti the cavalry.