Thornton was camping alone because he had frozen his feet and his partners had left him behind to recuperate. They themselves had gone on ahead, and Thornton, who was much better by the time he met Buck, was just waiting for his partners to return for him with a raft that was to carry them on to Dawson.
Thornton was the ideal master because while "other men saw to the welfare of their dogs from a sense of duty and business expediency, he saw to the welfare of his as if they were his own chldren". Thornton truly loved his dogs, and cared about their well-being (Chapter 6).
After their long search, Thornton and his partners found gold. They set up camp and worked everyday panning for the precious metal, and there was little for the dogs to do. With little activity and long hours just to wander and think, Buck became restless and the call of the wild was awakened within him anew.
When he returned to camp from killing the moose, Buck found Thornton, his last tie to civilization, dead, and the camp overrun with Yeehats. With "overpowering rage...he lost his head...hurling himself upon (the Yeehats) in a frenzy to destroy". Hie attacked with such effective fury that the Yeehats were terrified and ran away, "proclaiming...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" (Chapter 7).