Buck, a large and handsome dog who is part St. Bernard and part Scotch sheep dog, lives on a sizable estate in California’s Santa Clara Valley. He is four years old and was born on the estate, which is owned by the wealthy Judge Miller. Buck is the undisputed master of Judge Miller’s place, as the locals call it, and is beloved by the Miller children and grandchildren. Buck has the run of the entire place, confident of his superiority to the pampered house pets and the fox terriers that live in the kennels.

But, unbeknownst to Buck, there is a shadow over his happy life. The year is 1897, and men from all over the world are traveling north for the gold rush that has hit the Klondike region of Canada, just east of Alaska. They need strong dogs to pull their sleds on the treacherous journey. Nor does Buck realize that Manuel, a gardener on Judge Miller’s estate, is an undesirable acquaintance. Manuel’s love of gambling in the Chinese lottery makes it difficult for him to support his wife and several children. One day, while the judge is away, Manuel takes Buck for a walk and leads him to a flag station where a stranger is waiting. Money changes hands, and Manuel ties a rope around Buck’s neck. When the rope is tightened, Buck attacks the stranger, but he finds it impossible to break free. The man fights him; Buck’s strength fails, and he blacks out and is thrown into the baggage car of the train.

When Buck regains consciousness, he feels himself being jolted around. He hears the whistle of the train and, from having traveled with the judge, recognizes the sensation of riding in a baggage car. He opens his eyes angrily and sees the kidnapper reaching for his throat. He bites the man’s hand and is thrown down and choked repeatedly, then locked into a cagelike crate. He stays there for the rest of the night, and, in the morning, his crate is carried out by four men. Buck is passed from vehicle to vehicle, neither eating nor drinking for two days and two nights. He grows angrier and resolves never to let his tormentors tie a rope around his neck again.

In Seattle, Buck’s crate is lifted into a small yard with high walls, while a stout man signs for him. Buck decides that this new man is his next tormentor and lunges at him inside the cage. The man smiles and brings out a hatchet and a club. He begins to break the crate, and the other men step back fearfully. Buck snarls and growls and leaps at the man with all his weight, but he feels a blow from the club. It is the first time he has been hit with a club, so he is both hurt and stunned, but he continues trying to attack until the man beats him into submission. Once Buck is exhausted and prostrate, the man brings him water and meat and pats him on the head. Buck understands that he does not stand a chance against a man with a club—it is his introduction into “primitive law,” where might makes right.

Buck watches other men arrive, sometimes taking other dogs away with them, and he is glad that he is not chosen. Buck’s time finally comes when a French Canadian named Perrault buys him and a Newfoundland bitch named Curly. They are taken onto a ship called the Narwhal and turned over to another French Canadian named Francois. They join two other dogs, Spitz and Dave, on the journey northward, and Buck realizes that the weather is growing colder. Finally, they arrive and step out onto a cold surface that Buck does not recognize, never having seen snow before.

The meaning of chapter titles in The Call of the Wild extends beyond a simple description of the plot. The first chapter, “Into the Primitive,” is concerned not only with Buck’s departure from civilization and his entrance into a more savage, primitive world, but also with the contrast between civilized life and primitive life. This contrast is strong throughout the novel, and the story of Buck’s adventures in the Klondike is largely the story of how he gradually sheds all the customs that define his earlier life in human society to become a creature of the wild, primal world of the north. Here, in the first days after his kidnapping, he takes the first steps away from his old life and toward a new one.

As the novel opens, he is clearly a creature of the civilized world, a world defined by gentility, order, and rules, and embodied by Judge Miller’s sprawling home in the “sun-kissed” Santa Clara Valley. Furthermore, Buck’s original owner is a judge, overseeing the fair rule of law that allows for civilized life. The judge’s estate is an “orderly array” of buildings, over which Buck rules almost from birth. Even though the arrangement is orderly, it is not necessarily democratic: Buck never won the right to rule, as he does later in the wild North, but rather inherited it, living the life of a "sated aristocrat." In this world, Buck is a pet rather than a servant; he does not work for or protect Judge Miller but exists as a companion and playmate. There is no struggle in this life, and no burdens that must be borne—there is only luxury and contentment.

Buck’s departure “into the primitive” begins to demonstrate a different kind of law, one in which birthright and aristocracy are meaningless. Throughout the novel, London contrasts the rules of the old world that Judge Miller inhabits with the laws of life in the harsh, wild Klondike. Buck learns the first of these laws when the man beats him with the club. “That club,” we are told, “was a revelation. It was his introduction to the reign of primitive law.” The central feature of that law, of course, is that might makes right—that the use of force is justified by the fact that it prevails over the lack of force or brutality. This philosophy develops throughout the novel, as Buck’s life becomes a harsh struggle for existence in which he must either kill or be killed. The club also teaches Buck, for the first time, that human beings can be the enemy, although the full implications of this knowledge remain to be considered.

The novel is told primarily from Buck’s point of view, filtered through the third-person omniscience of a narrator, and, although the protagonist of The Call of the Wild is a dog, he inspires a very humanlike empathy. London is not simply substituting an animal protagonist for a human one; he is particularly concerned with understanding the parallels between human life and animal life, which seem on the surface to be so different from each other. The novel suggests that, in their most primitive states, both human and animal are defined by a struggle for survival and mastery. In order to allow us to empathize with Buck as an animal narrator and see our own lives reflected in his, London gives his protagonist capacities that are normally reserved for humans. Buck is not merely a creature of instinct but is capable of wonder, concerned about justice, and able to feel shame. He is, much like the human beings who surround him, intensely self-conscious.