Dolly was in a pure moment of madness. Then he ran after Buck but François killed him with an axe.
Spitz tried to take advantage of the situation because Buck was really tired.
Buck was protecting the other dogs from the leader Spitz. One day, Pike didn't wanted to wake up but Spitz was looking for him. When Spitz found Pike, he fought with Pike and Buck suddenty came to defend Pike.
Looking for protection, all the dogs changed sides and went with Buck, every dog was scared of Spitz, but they knew that Buck could protect them from Spitz.
After a long fight, Buck killed Spitz at the last minute. Spitz died, but everyone else survived.