The Gold Rush in the Yukon and Alaska requires big, strong dogs that would be able to pull sledges over icy trails. Buck, a large animal living in the house of Judge Miller in Santa Clara, California, is exactly what the explorers want. He is an animal characterized by human- intelligence, strength and dignity. Thus he has enjoyed his civilized life with the occasional nature strolls or hunting trip. Manuel, a gardener's helper with tendencies for gambling and a need for money, manages to kidnap Buck and sells him on the black market. He is given to a saloon-keeper and transported to the Northland. Buck is kept in a cage and is starting to become increasingly angry. When he is taken out of the cage, he jumps at a man who got him out of it. But before he tries to bite him, the man hits him with the club.
Meeting the man and the painful encounter with his club pushes Buck into submission. He is not broken, but he has learnt that a man with a club is stronger than him. Buck with Dave and Curly, two other dogs, is sold to François and Perrault, two agents of the Canadian government. They have to travel to Dawson, Alaska and then back to Skagway. While Curly is killed in camp for trying to make friendly advances to a husky, Buck understands that this is the law of the club and fang which dominates the new life he is headed for. He resolves never to go down in that manner. Buck and Dave join a dog team led by Spitz, a husky dog. The trail work begins immediately. Buck learns fast from the other dogs. In some time he starts to become wilder, losing the domesticity. Tensions develop between him and Spitz. Buck is ready to be a leader, and to usurp Spitz's power. While hunting a rabbit one night, the two end up in a fight to the death. Buck achieves mastery. He will not be harnessed to the sledge unless he takes the leader position. Even the appearance of the club does not faze him, he has learned how to avoid that. When François allows him to take the position, it is triumphant because Buck no longer allows humans to completely control his fate. After a long period of travelling, dogs were very tired. But there was still a long way to go. They weren’t able to continue, so the team is sold to Hal, a young man who has no idea how to work with a dog team. His brother-in-law Charles and weepy sister Mercedes don’t help with anything. Because Hal is incompetent, they run out of food quickly. The dogs are starving and overworked. One by one they start to die.