Buck is the main character throughout, but we will encounter many important characters as the story progresses. In the beginning he lives with Judge Miller in the Santa Clara Valley. But most of the story takes place in the Klondike, during the gold rush., Because Buck is taken, and sold by the gardener. The main conflict of the story is, it we with who he loves, or do what he loves.
Buck has to fight Spitz in order to gain control of the pack. There are many other things that happen from the exposition to the climax, but i felt that this was a pretty important event in the story.
Buck goes away for a while with a wolf friend that he made, when he comes back he find all the other dogs and people including John Thornton dead. He sees the Yeehats and runs straight for the leader, and rips out his throat. Then he continues killing more and more of them until the remaining ones left in a hurry.
John Thornton died in the battle with the Yeehats, after Buck fights the remaining ones off, he doesn't do much for the next couple of days except for mourn over John.
After John Thornton died, man and claims of man no longer bound Buck. The wolf pack that had followed the Yeehats, had invaded Buck's Valley. Buck fought off the the pack for an hour and a half, ripping 0ut throats and slashing shoulders. To prevent them from getting behind him he kept backing up, they pushed him down until he was cornered. One of them came up in a friendly manor, Buck recognized him and they touched noses. Then an old one came forward, snarled his lips, then sat and howled.