Buck, the novel's protagonist; a 140-pound St. Bernard–Scotch Collie mix who lived contentedly in California with Judge Miller. However, he was stolen and sold to the Klondike by the gardener's assistant Manuel and was forced to work as a sled dog in the harsh Yukon. He eventually finds a loving master named John Thornton and gradually grows feral as he adapts to the wilderness, eventually joining a wolf pack. After Thornton's death, he is free of humans forever and becomes a legend in the Klondike.