Buck lives in California, and people love him. But one day, he is captured by a man that wants to sell him to prospectors in the Yukon.
In the voyage, a member of the crew, beats him with a club. Then he is sell to Francoise and Perrault, to pull a sled full of mails to deliver with other dogs. The boss of the dogs is a husky named Spitz.
Buck gains the trust of Perrault and Francois and the other dogs, but it can be only one leader of the dogs, so Spitz faces Buck in a duel. Buck wins and Spitz run away, so Buck is the new leader.
But one day, the mail route is replaced by the telegraph, a new invention to send mails, so he sell the dogs.Hal, an inexperienced gold prospector, buys the dogs and gradually works them to exhaustion carrying a heavy load in weather unsuitable for sledding.
The exhausted dogs stop to rest before Hal can force them to cross an unstable frozen lake. When Buck refuses to move, Hal threatens to shoot him. Thornton appears and rescues Buck while Hal forces the other sled dogs to cross the lake. Under Thornton's care, Buck recovers. Later, at a saloon, Thornton is attacked by Hal, who reveals the dogs managed to run off leaving him with nothing. Buck and Thornton then travel beyond the Yukon map where they can freely live in the wild. They come across an abandoned cabin in an open valley and settle in. Meanwhile, Hal relentlessly hunts them, believing Thornton is hiding gold.
In the open wilderness, Thornton and Buck bond over their daily activities, primarily fishing and gold panning. Throughout their time together, Buck meet a female white wolf. Going back and forth between Thornton and the white wolf, Buck is conflicted by his domesticated life with Thornton and his place with the wolf pack that the female belongs to. Thornton believes it is time to return home and tells Buck he is leaving in the morning, and to come and say good-bye. Buck heads into the forest and sleeps beside the white wolf, clearly conflicted. Hal subsequently finds and shoots Thornton. Buck returns and kills Hal by pushing him into the cabin, which has caught on fire. Thornton wants Buck to live for himself. He reassures him with his final words, "It's okay, boy. You're home."
Buck returns to the wilderness. There, he have childs with the white wolf and becomes the pack leader, fully embracing the call of the wild.