After reaching Dawson, the team returns to Skagway. The journey takes one month. The dogs are worn out; Buck has lost twenty-five pounds in weight. Within four days, Buck and his mates are sold to Charles, a middle-aged man, and Hal, a man of about nineteen. Traveling with the men is Mercedes, who is Charles's wife and Hal's sister. Buck's new owners are incompetent, and overload the sled. The dogs are unable to move it. Hal calls them lazy and whips them, although Mercedes tries to persuade him not to. An onlooker suggests that Hal help the dogs by freeing the runners of the sled that are frozen to the snow. When this is done, the dogs are able to pull the sled, but it is so badly loaded it overturns. The owners reluctantly cut the load in half, and acquire six more dogs, making a total of fourteen. The newcomers are not much use, however, and nor does Buck have his heart in the work. He knows he cannot depend on his new masters, because they do not know how to do anything. Progress is very slow, and dog food runs short. Half the food goes when only a quarter of the distance has been covered. One of the dogs, Dub, is injured, and Hal shoots him. Six dogs die of starvation. As the going gets tougher, the three travelers fall to quarreling. Mercedes insists on riding on the sled, which adds intolerably to the load pulled by the weak and starving dogs. Hal, Charles and Mercedes are insensitive to the suffering of the animals. But the seven remaining dogs continue to pull the sled, despite their ill-treatment. One day Billie collapses and cannot continue. Hal kills him with an axe. The next day Koona dies, and only five remain.
It is spring time, but the travelers are in such a desperate situation they do not notice it. The ice on the river is beginning to break up, but they manage to reach the camp of John Thornton at the mouth of White River. Thornton tells them to take no more chances on the melting ice. Hal refuses to take his advice and wants to continue. But he cannot persuade his exhausted dogs to get up, so he whips them until they begin to move. But Buck refuses. Hal beats him with a club, but Buck has made a decision not to get up. Thornton intervenes, striking Hal, and telling Hal he will kill him if he hits the dog again. Hal draws a knife, but Thornton knocks it out of his hand.
Hal decides to make off without Buck. They pull out from the bank and start off down the river. After a quarter of a mile, the ice breaks up and the men and dogs are all drowned.
Charles, Hal and Mercedes are the opposite of the grizzled but efficient Fran�ois and Perrault. They cannot adapt to their new, harsh Arctic environment, as is shown when they overload the sled because they want to take all the trappings of their former, more civilized life-canned goods, blankets, dishes-with them. They consistently exercise bad judgment, so it is natural, according to the law of the survival of the fittest, that they should perish.
In this episode, London contrasts the civilized and primitive worlds, to the advantage of the latter. The "civilized" trio from the south are foolish, petty and endlessly quarrelsome. They are unable to learn and refuse to accept good advice. They degenerate into callous, cruel behavior to their dogs. The more their troubles accumulate, the worse they behave to each other and to their dogs. They know nothing of what London describes as "the wonderful patience of the trail which comes to men who toil hard and suffer sore, and remain sweet of speech and kindly."
The episode also illustrates Buck's preternatural instincts in refusing to go on the final, fatal trip. He has a wild animal's instinct for danger. However, he is not yet ready to answer fully the call of the wild. In his state of exhaustion and near starvation, he still needs the nurturing care of a human. This he will find in John Thornton, who rescues him.