Buck, a huge, four-year-old half-Saint Bernard and half-Scottish shepherd dog, is living a life of civilized ease in California's Santa Clara Valley in the home of Judge Miller. It seems to be the best of all possible worlds, for Buck is the most prized animal that the Judge owns. Around this time, however, gold is discovered in the great North, and large dogs suddenly become tremendously valuable because these types of dogs are needed to haul the heavy sleds through the deep snow fields.