New Yorker David Kingston, a university student involved in the study of mine engineering, is falsely accused of theft and expelled from school. David's mother soon dies of grief, and he decides to end it all by jumping in the river. David is deterred from suicide, however, when he adopts a stray pup, which he names "Thunder." The dog later finds a map indicating the location of a gold mine, and David heads west to Northern California.

Thunder, a dog raised by Ellen, a sheepherder's daughter, is driven to the wilderness by the brutal treatment of her father, Bill Garside, and becomes an outlaw; when grown, he takes command of a wolfdog pack. Later, Ellen, driven from her home by the same brutal herder, seeks refuge at the cabin of Neal Barrett, the forest ranger; she is pursued by the hungry pack and is stranded on a rocky cliff where Thunder once again encounters his former mistress. He challenges the pack in her defense, provoking a battle between himself and a rival for his command. Later, Thunder rescues Ellen from her brutal father.

A loyal German Shepherd dog follows his master to the French front in World War One.

A dog named Thunder, the weakling of his brood, is born in a lumber camp in the North Woods, operated by Anita Baker. The cowardly dog is cast out of the camp and adopted by forest ranger Allen Gregory. Meanwhile, Bill Martin, the brutal camp superintendent, covets both Anita and her property. When Bill attacks Anita, Thunder comes to the rescue and proves his courage by warding off the villain.

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.

Stanley Gilmore, the son of a railroad president, atones for a series of wild escapades by traveling to Tennessee to secure a right-of-way through the property of farmer Dave Wade. Accompanied by his dog, Thunder, Stanley meets with Dave and initiates a friendship with the farmer's daughter, Patsy.

The Kid and his pals are horse thieves wanted by the law. As he takes a horse from Jan Walton she makes him promise to bring it back.

A WWI drama in which a Red Cross dog saves a man.