Animal lover Davey Dawson (Sammy McKim) has no idea that his stepfather (J.P. McGowan) and his cronies are poaching bears in the nearby Blackstone National Park. But the Three Mesquiteers -- Tucson Smith (Ray Corrigan), Stony Brooke (Robert Livingston) and Lullaby Joslin (Max Terhune) -- are wise to the criminals' deeds. But when a ranger is shot and Stony is framed for the crime, it's up to Lullaby and Tucson to prove his innocence.