Synopsis: The Three Mesquiteers - Tucson, Stony and Lullaby - and the Blackstone National Park Rangers are having a bit of a disagreement. The rangers refuse to allow guns on their property.The Mesquiteers are upset that mountain lions and bears are killing cattle. Young Davey maintains an animal sanctuary in his stepfather's barn, but Davey doesn't know that his stepfather and his henchmen are poaching animals and rustling cattle. The Three Mesquiteers finally corner the gang, but a ranger is shot in the back and Stony is framed for his killing. The daring Mesquiteers must prove Stony's innocence while fighting bears, fires, and wily rustlers.