When Buck earned sixteen hundred dollars in five minutes for John Thornton, he made it possible for his master to pay off certain debts and to journey with his partners into the East after a fabled lost mine. John Thornton, and Pete and Hans, with Buck and half a dozen other dogs, set off into the East on an unknown trail to achieve where men and dogs as good as themselves had failed. They sledded seventy miles up the Yukon, swung to the left into the Stewart River, passed the Mayo and the McQuestion, and held on until the Stewart itself became a streamlet, threading the upstanding peaks which marked the backbone of the continent.

 John Thornton asked little of man or nature. He was unafraid of the wild. With a handful of salt and a rifle he could plunge into the wilderness and fare wherever he pleased and as long as he pleased. Being in no haste, Indian fashion, he hunted his dinner in the course of the day's traveling; and if he failed to find it, like the Indian, he kept on travelling, secure in the knowledge that sooner or later he would come to it. So, on this great journey into the East, straight meat was the bill of fare, ammunition and tools principally made up the load on the sled, and the time-card was drawn upon the limitless future.

 To Buck it was boundless delight, this hunting, fishing, and indefinite wandering through strange places. For weeks at a time they would hold on steadily, day after day; and for weeks upon end they would camp, here and there, the dogs loafing and the men burning holes through frozen muck and gravel and washing countless pans of dirt by the heat of the fire. Sometimes they went hungry, sometimes they feasted riotously, all according to the abundance of game and the fortune of hunting. Summer arrived, and dogs and men, packs on their backs, rafted across blue mountain lakes, and descended or ascended unknown rivers in slender boats whipsawed from the standing forest.

 The months came and went, and back and forth they twisted through the uncharted vastness, where no men were, and yet where men had been, if the Lost Cabin were true. And through another winter they wandered on the obliterated trails of men who had gone before. 

 Spring came on once more, and at the end of all their wandering they found, not the Lost Cabin, but a shallow placer in a broad valley where the gold showed like yellow butter across the bottom of the washing-pan. They sought no farther. Each day they worked earned them thousands of dollars in clean dust and nuggets, and they worked every day. The gold was sacked in moose-hide bags, fifty pounds to the bag, and piled like so much firewood outside the spruce-bough lodge. 

Buck loved to run in the dim twilight of the summer midnights, listening to the subdued and sleepy murmurs of the forest, reading signs and sounds as man may read a book, and seeking for the mysterious something that called--called, waking or sleeping, at all times, for him to come. One night he sprang from sleep with a start, eager-eyed, nostrils quivering and scenting, his mane bristling in recurrent waves. From the forest came the call , distinct and definite as never before,--a long-drawn howl, like, yet unlike, any noise made by husky dog. And he knew it, in the old familiar way, as a sound heard before. He sprang through the sleeping camp and in swift silence dashed through the woods. As he drew closer to the cry he went more slowly, with caution in every movement, till he came to an open place among the trees, and looking out saw, erect on haunches, with nose pointed to the sky, a long, lean, timber wolf.

He had made no noise, yet it ceased from its howling and tried to sense his presence. Buck stalked into the open, half crouching, body gathered compactly together, tail straight and stiff, feet falling with unwonted care. Every movement advertised commingled threatening and overture of friendliness. It was the menacing truce that marks the meeting of wild beasts that prey. But the wolf fled at sight of him. He followed, with wild leapings, in a frenzy to overtake. He ran him into a blind channel, in the bed of the creek where a timber jam barred the way. The wolf whirled about, pivoting on his hind legs after the fashion of Joe and of all cornered husky dogs, snarling and bristling, clipping his teeth together in a continuous and rapid succession of snaps. 

Buck did not attack, but circled him about and hedged him in with friendly advances. The wolf was suspicious and afraid; for Buck made three of him in weight, while his head barely reached Buck's shoulder. Watching his chance, he darted away, and the chase was resumed. Time and again he was cornered, and the thing repeated, though he was in poor condition, or Buck could not so easily have overtaken him. He would run till Buck's head was even with his flank, when he would whirl around at bay, only to dash away again at the first opportunity.

But in the end  the wolf, finding that no harm was intended, finally sniffed noses with him. Then they became friendly, and played about in the nervous, half-coy way with which fierce beasts belie their fierceness. After some time of this the wolf started off at an easy lope in a manner that plainly showed he was going somewhere. He made it clear to Buck that he was to come, and they ran side by side through the sombre twilight, straight up the creek bed, into the gorge from which it issued, and across the bleak divide where it took its rise.

They ran steadily, hour after hour, the sun rising higher and the day growing warmer. Buck was wildly glad. He knew he was at last answering the call, running by the side of his wood brother toward the place from where the call surely came. 

They stopped by a running stream to drink, and, stopping, Buck remembered John Thornton. He sat down. The wolf started on toward the place from where the call surely came, then returned to him, sniffing noses and making actions as though to encourage him. But Buck turned about and started slowly on the back track. For the better part of an hour the wild brother ran by his side, whining softly. Then he sat down, pointed his nose upward, and howled. It was a mournful howl, and as Buck held steadily on his way he heard it grow faint and fainter until it was lost in the distance.

John Thornton was eating dinner when Buck dashed into camp and sprang upon him in a frenzy of affection, overturning him, scrambling upon him, licking his face, biting his hand--"playing the general tom-fool," as John Thornton characterized it, the while he shook Buck back and forth and cursed him lovingly.

For two days and nights Buck never left camp, never let Thornton out of his sight. He followed him about at his work, watched him while he ate, saw him into his blankets at night and out of them in the morning. But after two days the call in the forest began to sound more imperiously than ever. Buck's restlessness came back on him, and he was haunted by recollections of the wild brother, and of the smiling land beyond the divide and the run side by side through the wide forest stretches. Once again he took to wandering in the woods, but the wild brother came no more; and though he listened through long vigils, the mournful howl was never raised.

He began to sleep out at night, staying away from camp for days at a time; and once he crossed the divide at the head of the creek and went down into the land of timber and streams. There he wandered for a week, seeking vainly for fresh sign of the wild brother, killing his meat as he traveled and traveling with the long, easy lope that seems never to tire. He fished for salmon in a broad stream that emptied somewhere into the sea, and by this stream he killed a large black bear, blinded by the mosquitoes while likewise fishing, and raging through the forest helpless and terrible.

A carnivorous animal living on a straight meat diet, he was in full flower, at the high tide of his life, overspilling with vigor and virility. When Thornton passed a caressing hand along his back, a snapping and crackling followed the hand, each hair discharing its pent magnetism at the contact. Every part, brain and body, nerve tissue and fibre, was keyed to the most exquisite pitch.

As the fall of the year came on, the moose appeared in greater abundance, moving slowly down to meet the winter in the lower and less rigorous valleys. Buck had already dragged down a stray part-grown calf; but he wished strongly for larger and more formidable quarry, and he came upon it one day on the divide at the head of the creek. A band of twenty moose had crossed over from the land of streams and timber, and chief among them was a great bull. He was in a savage temper, and, standing over six feet from the ground, was as formidable an antagonist as even Buck could desire. Back and forth the bull tossed his great palmated antlers, branching to fourteen points and embracing seven feet with the tips. His small eyes burned with a vicious and bitter light, while he roared with fury at sight of Buck.

From the bull's side, just forward of the flank, protruded a feathered arrow-end, which accounted for his savageness. Guided by that instinct which came from the old hunting days of the primordial world, Buck proceeded to cut the bull out from the herd. It was no slight task. He would bark and dance about in front of the bull, just out of reach of the great antlers and of the terrible splay hoofs which could have stamped his life out with a single blow. Unable to turn his back on the fanged danger and go on, the bull would be driven into paroxysms of rage. At such moments he charged Buck, who retreated craftily, luring him on by a simulated inability to escape. But when he was thus separated from his fellows, two or three of the younger bulls would charge back upon Buck and enable the wounded bull to rejoin the herd.

As the day wore along and the sun dropped to its bed in the northwest (the darkness had come back and the fall nights were six hours long), the young bulls retraced their steps more and more reluctantly to the aid of their beset leader. The down-coming winter was hurrying them on to the lower levels, and it seemed they could never shake off this tireless creature that held them back. Besides, it was not the life of the herd, or of the young bulls, that was threatened. The life of only one member was demanded, which was a remoter interest than their lives, and in the end they were content to pay the toll.

As twilight fell the old bull stood with lowered head, watching his mates as they shambled on at a rapid pace through the fading light and knew he could not follow.

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. 

At last, at the end of the fourth day, he pulled the great moose down. For a day and a night he remained by the kill, eating and sleeping, turn and turn about. Then, rested, refreshed and strong, he turned his face toward camp and John Thornton. He broke into the long easy lope, and went on, hour after hour, never at loss for the tangled way, heading straight home through strange country with a certitude of direction that put man and his magnetic needle to shame.

As he ran he became more and more conscious of the new stir in the land. There was life abroad in it different from the life which had been there throughout the summer. Several times he stopped and drew in the fresh morning air in great sniffs, reading a message which made him leap on with greater speed. He was oppressed with a sense of calamity happening, if it were not calamity already happened; and as he crossed the last watershed and dropped down into the valley toward camp, he proceeded with greater caution.

Three miles away he came upon a fresh trail that sent his neck hair rippling and bristling. It led straight toward camp and John Thornton. As Buck slid along with the obscureness of a gliding shadow, his nose was jerked suddenly to the side as though a positive force had gripped and pulled it. He followed the new scent into a thicket and found Nig. He was lying on his side, dead where he had dragged himself, an arrow protruding, head and feathers, from either side of his body.

A hundred yards farther on, Buck came upon one of the sled-dogs Thornton had bought in Dawson. This dog was thrashing about in a death-struggle, directly on the trail, and Buck passed around him without stopping. From the camp came the faint sound of many voices, rising and falling in a sing-song chant. Bellying forward to the edge of the clearing, he found Hans, lying on his face, feathered with arrows like a porcupine. At the same instant Buck peered out where the spruce-bough lodge had been and saw what made his hair leap straight up on his neck and shoulders. A gust of overpowering rage swept over him. He did not know that he growled, but he growled aloud with a terrible ferocity. For the last time in his life he allowed passion to usurp cunning and reason, and it was because of his great love for John Thornton that he lost his head.

The Yeehat Indians were dancing about the wreckage of the spruce-bough lodge when they heard a fearful roaring and saw rushing upon them an animal the like of which they had never seen before. It was Buck, a live hurricane of fury, hurling himself upon them in a frenzy to destroy. He sprang at the foremost man (it was the chief of the Yeehats), ripping the throat wide open till the rent jugular spouted a fountain of blood. He did not pause to worry the victim, but ripped in passing, with the next bound tearing wide the throat of a second man. There was no withstanding him. He plunged about in their very midst, tearing, rending, destroying, in constant and terrific motion which defied the arrows they discharged at him. In fact, so inconceivably rapid were his movements, and so closely were the Indians tangled together, that they shot one another with the arrows; and one young hunter, hurling a spear at Buck in mid air, drove it through the chest of another hunter with such force that the point broke through the skin of the back and stood out beyond. Then a panic seized the Yeehats, and they fled in terror to the woods, proclaiming as they fled the advent of the Evil Spirit.

And truly Buck was the Fiend incarnate, raging at their heels and dragging them down like deer as they raced through the trees. It was a fateful day for the Yeehats. They scattered far and wide over the country, and it was not till a week later that the last of the survivors gathered together in a lower valley and counted their losses. As for Buck, wearying of the pursuit, he returned to the desolated camp. He found Pete where he had been killed in his blankets in the first moment of surprise. Thornton's desperate struggle was fresh-written on the earth, and Buck scented every detail of it down to the edge of a deep pool. By the edge, head and fore feet in the water, lay Skeet, faithful to the last. The pool itself, muddy and discolored from the sluice boxes, effectually hid what it contained, and it contained John Thornton; for Buck followed his trace into the water, from which no trace led away.

All day Buck brooded by the pool or roamed restlessly about the camp. Death, as a cessation of movement, as a passing out and away from the lives of the living, he knew, and he knew John Thornton was dead. It left a great void in him, somewhat akin to hunger, but a void which ached and ached, and which food could not fill. At times, when he paused to contemplate the carcasses of the Yeehats, he forgot the pain of it; and at such times he was aware of a great pride in himself--a pride greater than any he had yet experienced. He had killed man, the noblest game of all, and he had killed in the face of the law of club and fang. He sniffed the bodies curiously. They had died so easily. It was harder to kill a husky dog than them. They were no match at all, were it not for their arrows and spears and clubs. Thenceforward he would be unafraid of them, except when they bore in their hands their arrows, spears, and clubs.

Night came on, and a full moon rose high over the trees into the sky, lighting the land till it lay bathed in ghostly day. And with the coming of the night, brooding and mourning by the pool, Buck became alive to a stirring of the new life in the forest other than that which the Yeehats had made. He stood up, listening and scenting. From far away drifted a faint, sharp yelp, followed by a chorus of similar sharp yelps. As the moments passed the yelps grew closer and louder. Again Buck knew them as things heard in that other world which persisted in his memory. He walked to the centre of the open space and listened. It was the call, the many-noted call, sounding more luringly and compelling than ever before. And as never before, he was ready to obey. John Thornton was dead. The last tie was broken. Man and the claims of man no longer bound him.

Hunting their living meat, as the Yeehats were hunting it, on the flanks of the migrating moose, the wolf pack had at last crossed over from the land of streams and timber and invaded Buck's valley. Into the clearing where the moonlight streamed, they poured in a silvery flood; and in the centre of the clearing stood Buck, motionless as a statue, waiting their coming. They were awed, so still and large he stood, and a moment's pause fell, till the boldest one leaped straight for him. Like a flash Buck struck, breaking the neck. Then he stood, without movement, as before, the stricken wolf rolling in agony behind him. Three others tried it in sharp succession; and one after the other they drew back, streaming blood from slashed throats or shoulders.

This was sufficient to fling the whole pack forward, pell-mell, crowded together, blocked and confused by its eagerness to pull down the prey. Buck's marvelous quickness and agility stood him in good stead. Pivoting on his hind legs, and snapping and gashing, he was everywhere at once, presenting a front which was apparently unbroken so swiftly did he whirl and guard from side to side. But to prevent them from getting behind him, he was forced back, down past the pool and into the creek bed, till he brought up against a high gravel bank. He worked along to a right angle in the bank which the men had made in the course of mining, and in this angle he came to bay, protected on three sides and with nothing to do but face the front.

And so well did he face it, that at the end of half an hour the wolves drew back discomfited. The tongues of all were out and lolling, the white fangs showing cruelly white in the moonlight. Some were lying down with heads raised and ears pricked forward; others stood on their feet, watching him; and still others were lapping water from the pool. One wolf, long and lean and gray, advanced cautiously, in a friendly manner, and Buck recognized the wild brother with whom he had run for a night and a day. He was whining softly, and, as Buck whined, they touched noses.

Then an old wolf, gaunt and battle-scarred, came forward. Buck writhed his lips into the preliminary of a snarl, but sniffed noses with him, Whereupon the old wolf sat down, pointed nose at the moon, and broke out the long wolf howl. The others sat down and howled. And now the call came to Buck in unmistakable accents. He, too, sat down and howled. This over, he came out of his angle and the pack crowded around him, sniffing in half-friendly, half-savage manner. The leaders lifted the yelp of the pack and sprang away into the woods. The wolves swung in behind, yelping in chorus. And Buck ran with them, side by side with the wild brother, yelping as he ran.

Each fall, when the Yeehats follow the movement of the moose, there is a certain valley which they never enter, a valley where they say an evil spirit lives.

In the summers there is one visitor, however, to that valley, of which the Yeehats do not know. It is a great, gloriously coated wolf, like, and yet unlike, all other wolves. He crosses alone from the smiling timber land and comes down into an open space among the trees. Here a yellow stream flows from rotted moose-hide sacks and sinks into the ground, with long grasses growing through it and vegetable mould overrunning it and hiding its yellow from the sun; and here he muses for a time, howling once, long and mournfully, before he leaves.