Pulling in dog teams, Buck travels along the ice of the Yukon River, carrying mail to and from the goldseekers of Dawson City, hundreds of mils at a time through the silent whiteness of the winter landscape.
Although he feels very close to his human masters, Buch begins to hear, more and more clearly, the Call of the Wild. This is the call to go back to a more primitive life in the forest, a life of long ago.
When he meets up with his wild brother the wolf, Buck faces the decision of his life.