Under Thornton's care, Buck recovers. Experiencing love for the first time, Buck comes to adore and admire Thornton as his "ideal master." Although the call beckons Buck into the forest, he remains devoted to Thornton, returning to his fireside, whenever tempted. Buck follows in loyal pursuit of Thornton when he rafts down towards Dawson with his two dogs, Skeet and Nig, and his human companions, Hans and Pete.
Buck's relationship with Thornton is unique because it is defined by love, making Thornton the "ideal master." Buck does not work for, or guard Thornton, but loves him. Yet this love is so potent that it enslaves Buck, quelling his instinctual desire to go into the forest and compelling him to follow Thornton wherever he may go.
One day, while resting on a steep cliff, Thornton tests Buck's loyalty by commanding him to jump off its ledge. Buck starts forward, but Thornton grabs him before he can toss himself over the edge. Buck's unwavering obedience delights and disturbs Thornton.
Buck's devotion to Thornton is so great that it is blind. While Buck lives for Thornton, he will also die for him. This steadfast obedience underlines Thornton's mastery over Buck.
Buck's devotion continues at Circle City, where Thornton gets into a bar fight with a hot-tempered man, called "Black" Burton. Buck comes to Thornton's defense, launching himself at Burton's throat. The bystanders set up a miner's court to try Buck for the offence, but "discharge" him, citing that he had "sufficient provocation." Buck establishes a reputation throughout Alaska for his loyalty.
Buck's attack on "Black" Burton shows that though Thornton has tamed Buck's heart, he has not entirely curbed Buck's fighting instincts. The court's ruling in Buck's favor cements the dominance of the law of club and fang in not just the natural world but also the human world of the Northland.
Buck proves his loyalty again when he saves Thornton's life later that year. During a boat launching, Thornton is flung out of the raft. The river's current sends Thornton into a stretch of wild rapids. Buck jumps in the water, Thornton grabs his tail, and they attempt to swim towards shore, but the current is too strong, so Thornton instructs Buck to leave him behind. Buck returns to shore, but Hans attaches a line of rope to Buck and he launches into the stream again and again, until Thornton's able to grab him and be pulled ashore, "battered," but alive.
When Buck rescues Thornton, he not only repays John for rescuing his life. He highlights the interdependence of man and dog in the wild. Man and dog rely on each other not only to live, but to survive in the face of nature's unforeseen calamities and conditions. That both Buck and Thornton are willing to risk their lives for the other shows that their relationship is one of mutual love and respect.
Buck gains even greater fame that winter in Dawson when he performs an incredible "exploit." In the Eldorado Saloon, Thornton boasts that Buck can start a sled with a thousand pounds, break it out of its runners, and "walk off." Matthewson, a rich prospector, wages one thousand dollars that Buck can't pull the sled. With his bluff called, Thornton doubts whether Buck can do it, but takes Matthewson up on his offer, borrowing one thousand dollars from his friend O'Brien to cover the wager.
Though Thornton may be the "ideal master" in Buck's eyes, he is far from flawless. On a selfish whim, he sets Buck up to take on a daunting task. That he risks Buck's well being to save his pride and grease his wallet, suggests that for a moment he views Buck as a source of pride and profit, casting an unsavory shadow on Thornton's otherwise loving mastership of Buck.
Onlookers assemble outside, where the men give odds, settling at three to one. Matthewson ups the bet six hundred dollars, and stresses that Buck must break the runners out of the ice in order for the wager to hold. Thornton harnesses him to the sled, carrying forty, twenty-five pound sacks of flour, and whispers to Buck, "As you love meÉ.As you love me."
Thornton redeems himself when he whispers, "As you love me." Instead of calling Buck to action through fear, or violence, Thornton appeals to Buck's love for him, showing that regardless of the outcome he will still cherish Buck. At the same time, Thornton's whisper is about Buck loving Thornton—the relationship is still about what man gets from dog a bit more than the other way around.
Thornton shouts directions at Buck to pull the sled. Straining under the traces, Buck swings to the right, then to the left, breaking the sled's runners out of the ice. Finally Buck lunges forward, pulling the sled with every fiber of his being, every ounce of his strength. He crosses the one hundred yard line, winning the bet. The crowd erupts in cheers, while Buck and Thornton share a moment of triumph. Buck nips his master, lovingly.
Pulling the sled is Buck's ultimate showing of loyalty and love for John Thornton. Buck serves in the traces one more time not because he is forced to, but because he loves John Thornton. Yet while love strengthens Buck enough to pull the sled, it still ties him closely to man's ownership.