As the book begins, Henry is alone because he has lost his dogs and his partner to ravenous wolves. has let his dogs run away. is lost in the wilderness. is chased into the wild by wolves while trying to find food.

Henry is alone because he is lost in the wilderness. Though there is no definite story or title of the book given, we assume that the answer to your question is that the character got lost by some events into the wilderness. It might be a book that's about the story of his triumphs and failures, and ultimately his survival. The plot is quite adventurous as it seems.