The author devotes the second half of Chapter 7 to telling most of the story about Storm, and a few lines into that section is a sentence that sums up the main idea of what he wants to say.  It reads, "Joy, loyalty, toughness, peacefulness - all of these were part of Storm". 

Storm was a tough and determined sled dog, insisting on pulling even when he was bleeding, as the author describes back in Chapter 2.  He liked to play and goof around with the other dogs and with the author as well, and would often hide things from him and make him laugh.  Storm had a special game with the author, in which he communicated that things were alright with a stick.  He would tell the author that things were not going well by refusing the stick, and would reassure him by playing with it when things were good.  Even when he died, tied up to his doghouse, he wanted to tell the author that he was not upset at being restrained at that final moment - faithful Storm died quietly with his stick in his mouth in what the author interpreted as a peaceful and loving good-bye.