Hopalong Cassidy and Johnny Nelson ride to the mountains to help a man and his daughter save their logging business from someone who is sabotaging their efforts.
Buck Peters arranges for Hoppy, California, Johnny and other cowboys to go to the aid of friends whose cattle are being rustled. Hoppy and California locate the rustlers' hideout and join the gang by posing as outlaws themselves, but must find a way to let the rest of the posse know where they are.
Hopalong Cassidy guide une équipe d'archéologues sur le site d'une mésa indienne abandonnée. Arrivés sur le site, ils s'aperçoivent qu'ils sont suivis par une bande de despérados, tandis que les chinois, habitants d'une ville proche, semblent tout mettre en œuvre pour décourager l'expédition.
Hoppy, California and Johnny come to the ranch of a friend and his daughter, disguised as dude detectives from the east, to investigate the disappearances, without a trace, of several herds of cattle.
Jimmy's father, a rancher, died in suspicious circumstances. To make things worse, Jimmy's disreputable uncle has a plot to take over the ranch. Jimmy turns to his friend Brad, the Marshal, for help.