Thirty days later, the dogs and men arrive back at Skaguay, exhausted and worn down. The drivers expect a long stopover in the town, but they are ordered to deliver more mail right away. The dogs are replaced with a fresh team, and Buck and his mates are sold to two men recently arrived from the States. The new owners, Hal and Charles, are less organized and professional than the previous drivers; Hal carries a knife and a heavy gun, but they are obviously inexperienced and out of place in the Northland.

They load up the sled together with Charles’s wife, Mercedes, a spoiled, pampered woman who is also Hal’s sister. Laden with all their possessions—pots and pans, clothes and tents—the sled is too heavy to be pulled. Hal tries to whip the team, but the dogs still cannot pull the sled, even when Mercedes pleads with them to pull so that her brother will stop whipping them. An onlooker tells them to break out the frozen runners, and this time the sled moves ahead; but as they hit a steep slope, half the load slips off. Angry, Buck keeps running, with the other dogs following his lead.

Friendly townspeople help collect the goods and the dogs and advise Hal to carry less stuff and get more dogs. The load is cut in half but remains heavy. Charles and Hal buy six more dogs, but the new animals are inexperienced. Buck is generally unhappy with these new owners, who are lazy and sloppy. They travel much more slowly than they expected, because of the owners’ disorganization and Mercedes’ demands. To make matters worse, they overfeed the dogs at first, then underfeed them when they realize that they are running out of food. One dog, already injured, dies quickly when the food begins to run out, and the new dogs, weak and unused to the North, all begin to starve. Hal, Charles, and Mercedes squabble among themselves and show little compassion for the animals. Mercedes, in particular, constantly picks fights with the men and insists on riding the sled, increasing the weight and making them travel much more slowly.

At the Five Fingers, a stop along the route to Dawson, the dog food runs out, and the dog owners feed their team horsehide instead of meat. Buck pulls as long as he can and then falls down until the whip or club makes him pull again. He has wasted away from starvation and exhaustion, as have his fellows, who drop quickly. The new dogs die, and so does Billee. Soon only five dogs remain alive in the team, and these five are close to starvation. Meanwhile, springtime has come to the region, and all around them the snow and ice begins to melt.

Eventually, the team reaches John Thornton’s camp, where Thornton, an experienced gold hunter, tells them that the ice is melting and that they cannot push on without risking falling through. Hal ignores him and forces the dogs back into harness by whipping them cruelly. Buck, however, refuses to get up, sensing disaster lurking ahead on the trail, even as blows come from Hal’s whip and club. Near death, he has stopped feeling any pain. Suddenly, Thornton—who has been watching the entire display—leaps up, pushes Hal back, and stands over Buck, threatening to kill Hal if he strikes the dog again. Hal pulls out his knife, but Thornton knocks it from his hand with the handle of an ax. He cuts Buck out of his traces, and the rest of the team staggers on, dragging the sled across the snow.

John looks Buck over, checking for broken bones, but finds him simply exhausted, starved, and bruised. They watch the sled crawl over the ice. A quarter of a mile away, they suddenly see its back end drop down and hear Mercedes scream. Charles turns to run back, but then a section of ice gives way and the whole sled, dogs and humans included, drops down and disappears into the dark water.

Hal, Charles, and Mercedes demonstrate one way that civilization can be more harrowing than wilderness. So far, in the wild North, Buck has been blessed with experienced and sometimes even kind masters. With this trio, however, he experiences the dark side of the human-dog relationship. But the three newcomers are more than simply representative “bad masters.” Through the three characters, London exposes the worst side of civilization: its vanity, foolishness, stubbornness, and self-absorption along with a cosmopolitan idiocy that is uninformed by the wisdom of the wild.

From their first appearance, Hal, Charles, and Mercedes are presented as stereotypical “greenhorns”—newcomers in a frontier world and woefully out of place. Where the dog-breaker needed only a club to train Buck, Hal carries both a gun and a huge knife. Neither of these items do him any good, since one is traded for much-needed food on the trail, and Thornton easily knocks the other out of his hand during their confrontation. Both Hal and Charles, London writes, possess “a callowness sheer and unutterable.” They are absurd figures, and the addition of the whining, spoiled Mercedes only makes matters worse. She and Curly are the only female characters in the book, and neither lasts long. Their early demises may be London’s way of suggesting that women are ill-suited for primitive life; it is also possible that London is arguing that culture, by cultivating an ideal of helplessness, denies women the possibility of fully developing their potential. “It was her custom to be helpless,” he writes of Mercedes, and such helplessness has no place in the Arctic.

In another place, this trio would be merely absurd, with their constant bickering over various family grudges and general incompetence. But in the wild, incompetence proves deadly. When Hal and Charles wrongly calculate how much food they need by egregiously underestimating the time it will take to reach Dawson, their mistake has devastating consequences for themselves and especially for Buck and the other dogs. Their miscalculation causes the dark side of the human-animal relationship to manifest itself—Buck may be a Nietzschean superman of a dog, but he is still dependent on the wisdom of his human masters. Similarly, Arctic travel, for Mercedes and her men, is “a reality too harsh for their manhood and womanhood.” Because of the trio’s weakness, the dogs begin to starve, and this chapter, aptly titled “The Toil of Trace and Trail,” lingers over the horror of their journey, as most of them die and Buck is reduced to a bruised wreck of his former self. Yet, even in this extremity, London reminds us of his protagonist’s indomitable spirit. “It was heartbreaking,” he writes, “only Buck’s heart was unbreakable.”

Still, Buck’s dying body requires a savior, which appears in the form of John Thornton. Whereas Hal, Charles, and Mercedes are creatures of comfort and civilization, Thornton is a man of the wild country, with all the wisdom of the North at his disposal. Aware of the dangers, Thornton urges the dog owners to halt; Hal, entirely unaware of these dangers, insists that they must go on. Only Buck escapes the final disaster, both because his strong spirit defies Charles and because his connection to the primitive world allows him to sense impending doom. But he still needs Thornton to save him; he has suffered through the worst that humanity has to offer, but he is not yet ready, or physically strong enough, to break with mankind and go into the true wild.