Eddie Phillips works for his father, an oilman searching for deposits in the north woods. A puppy intended for Eddie falls out of the truck that's transporting him and is stranded in the forest, but the pup learns to survive on his own and soon becomes master of his domain. A year or so later Eddie and another dog, White Fawn, happen to be camping near property owned by pretty young Betty Francisco when swindler Jim Mason discovers oil deposits on Betty's land the tries to swindle her out of them, but the heroic dog, now named Thunder, determines to stop Mason and Eddie helps him, not knowing that Thunder is the dog originally meant for him.