It was beautiful spring weather, but neither dogs nor humans were aware of it. Each day the sun rose earlier and set later. It was dawn by three in the morning, and twilight lingered till nine at night. The whole long day was a blaze of sunshine. The ghostly winter silence had given way to the great spring murmur of awakening life. This murmur arose from all the land, fraught with the joy of living. It came from the things that lived and moved again, things which had been as dead and which had not moved during the long months of frost. The sap was rising in the pines. The willows and aspens were bursting out in young buds. Shrubs and vines were putting on fresh garbs of green. Crickets sang in the nights, and in the days all manner of creeping, crawling things rustled forth into the sun. Partridges and woodpeckers were booming and knocking in the forest. Squirrels were chattering, birds singing, and overhead honked the wild–fowl driving up from the south in cunning wedges that split the air.

From every hill slope came the trickle of running water, the music of unseen fountains. All things were thawing, bending, snapping. The Yukon was straining to break loose the ice that bound it down. It ate away from beneath; the sun ate from above. Air–holes formed, fissures sprang and spread apart, while thin sections of ice fell through bodily into the river. And amid all this bursting, rending, throbbing of awakening life, under the blazing sun and through the soft–sighing breezes, like wayfarers to death, staggered the two men, the woman, and the huskies.

With the dogs falling, Mercedes weeping and riding, Hal swearing innocuously, and Charles's eyes wistfully watering, they staggered into John Thornton's camp at the mouth of White River. When they halted, the dogs dropped down as though they had all been struck dead. Mercedes dried her eyes and looked at John Thornton. Charles sat down on a log to rest. He sat down very slowly and painstakingly what of his great stiffness. Hal did the talking. John Thornton was whittling the last touches on an axe–handle he had made from a stick of birch. He whittled and listened, gave monosyllabic replies, and, when it was asked, terse advice. He knew the breed, and he gave his advice in the certainty that it would not be followed.

He was older than the days he had seen and the breaths he had drawn. He linked the past with the present, and the eternity behind him throbbed through him in a mighty rhythm to which he swayed as the tides and seasons swayed. He sat by John Thornton's fire, a broad–breasted dog, white–fanged and long–furred; but behind him were the shades of all manner of dogs, half–wolves and wild wolves, urgent and prompting, tasting the savor of the meat he ate, thirsting for the water he drank, scenting the wind with him, listening with him and telling him the sounds made by the wild life in the forest, dictating his moods, directing his actions, lying down to sleep with him when he lay down, and dreaming with him and beyond him and becoming themselves the stuff of his dreams.

So peremptorily did these shades beckon him, that each day mankind and the claims of mankind slipped farther from him. Deep in the forest a call was sounding, and as often as he heard this call, mysteriously thrilling and luring, he felt compelled to turn his back upon the fire and the beaten earth around it, and to plunge into the forest, and on and on, he knew not where or why; nor did he wonder where or why, the call sounding imperiously, deep in the forest. But as often as he gained the soft unbroken earth and the green shade, the love for John Thornton drew him back to the fire again.

Thornton alone held him. The rest of mankind was as nothing. Chance travellers might praise or pet him; but he was cold under it all, and from a too demonstrative man he would get up and walk away. When Thornton's partners, Hans and Pete, arrived on the long–expected raft, Buck refused to notice them till he learned they were close to Thornton; after that he tolerated them in a passive sort of way, accepting favors from them as though he favored them by accepting. They were of the same large type as Thornton, living close to the earth, thinking simply and seeing clearly; and ere they swung the raft into the big eddy by the saw–mill at Dawson, they understood Buck and his ways, and did not insist upon an intimacy such as obtained with Skeet and Nig.

As twilight fell the old bull stood with lowered head, watching his mates–the cows he had known, the calves he had fathered, the bulls he had mastered–as they shambled on at a rapid pace through the fading light. He could not follow, for before his nose leaped the merciless fanged terror that would not let him go. Three hundredweight more than half a ton he weighed; he had lived a long, strong life, full of fight and struggle, and at the end he faced death at the teeth of a creature whose head did not reach beyond his great knuckled knees.

From then on, night and day, Buck never left his prey, never gave it a moment's rest, never permitted it to browse the leaves of trees or the shoots of young birch and willow. Nor did he give the wounded bull opportunity to slake his burning thirst in the slender trickling streams they crossed. Often, in desperation, he burst into long stretches of flight. At such times Buck did not attempt to stay him, but loped easily at his heels, satisfied with the way the game was played, lying down when the moose stood still, attacking him fiercely when he strove to eat or drink.

The great head drooped more and more under its tree of horns, and the shambling trot grew weak and weaker. He took to standing for long periods, with nose to the ground and dejected ears dropped limply; and Buck found more time in which to get water for himself and in which to rest. At such moments, panting with red lolling tongue and with eyes fixed upon the big bull, it appeared to Buck that a change was coming over the face of things. He could feel a new stir in the land. As the moose were coming into the land, other kinds of life were coming in. Forest and stream and air seemed palpitant with their presence. The news of it was borne in upon him, not by sight, or sound, or smell, but by some other and subtler sense. He heard nothing, saw nothing, yet knew that the land was somehow different; that through it strange things were afoot and ranging; and he resolved to investigate after he had finished the business in hand.

From then on it was war between them. Spitz, as lead–dog and acknowledged master of the team, felt his supremacy threatened by this strange Southland dog. And strange Buck was to him, for of the many Southland dogs he had known, not one had shown up worthily in camp and on trail. They were all too soft, dying under the toil, the frost, and starvation. Buck was the exception. He alone endured and prospered, matching the husky in strength, savagery, and cunning. Then he was a masterful dog, and what made him dangerous was the fact that the club of the man in the red sweater had knocked all blind pluck and rashness out of his desire for mastery. He was preeminently cunning, and could bide his time with a patience that was nothing less than primitive.

It was inevitable that the clash for leadership should come. Buck wanted it. He wanted it because it was his nature, because he had been gripped tight by that nameless, incomprehensible pride of the trail and trace–that pride which holds dogs in the toil to the last gasp, which lures them to die joyfully in the harness, and breaks their hearts if they are cut out of the harness. This was the pride of Dave as wheel–dog, of Sol–leks as he pulled with all his strength; the pride that laid hold of them at break of camp, transforming them from sour and sullen brutes into straining, eager, ambitious creatures; the pride that spurred them on all day and dropped them at pitch of camp at night, letting them fall back into gloomy unrest and uncontent. This was the pride that bore up Spitz and made him thrash the sled–dogs who blundered and shirked in the traces or hid away at harness–up time in the morning. Likewise it was this pride that made him fear Buck as a possible lead–dog. And this was Buck's pride, too.

He openly threatened the other's leadership. He came between him and the shirks he should have punished. And he did it deliberately. One night there was a heavy snowfall, and in the morning Pike, the malingerer, did not appear. He was securely hidden in his nest under a foot of snow. Francois called him and sought him in vain. Spitz was wild with wrath. He raged through the camp, smelling and digging in every likely place, snarling so frightfully that Pike heard and shivered in his hiding–place.