The book starts out with Kazan, 1/4 wolf and 3/4 husky, who goes up north to the Canadian wilderness with his owner Thorpe where they are greeted by a man known as McCready. From the evidence in the beginning, it is shown that McCready knows Kazan from before, then named Pedro, and that the former was abusive to the latter. When McCready attacks Thorpe's wife Isobel, Kazan kills him and then runs away fearing the harsh punishment for killing a man. He later encounters a wolf pack of which he becomes the new leader, and has a mate, a young female gray wolf.
One day, the pack comes across the tracks of a sick old man, Pierre Radisson, his married daughter Joan and her child, a baby girl, and gets ready for the hunt. However, upon seeing the woman, Kazan turns against his pack, protecting the family from the other wolves. Eventually the whole pack with the exception of Gray Wolf runs away leaving Kazan and his loyal mate. As a gratitude for his help, Joan and her father take Kazan and heal him from his severe wounds. Soon after, when Kazan has recovered enough, his new owners start their journey to the city of Churchill, but Gray Wolf follows them at a distance with the hope to be reunited with Kazan. While on their way, Pierre dies, leaving his daughter and Kazan with no choice but to travel all alone. At the end of their strength, Kazan and Joan finally reach her husband cabin. From there on, he spends the entire winter staying with Gray Wolf for the days and sleeping at the cabin during the nights.
One day, as the spring advances, Kazan goes to see his companion only to find the great change: that she is a mother of three, and he is a father for the first time in his life. He acts accordingly to the new turn of his life, staying longer with Gray Wolf and even hunting for her, and spending less time with Joan. But when he returns from one of his hunts, Kazan finds out a lynx is fighting his companion. Kazan attacks the other predator and soon kills it. But then he discovers his cubs are dead and their mother is blinded for life.
Few days later, Joan and her husband are ready to leave and have decided to take Kazan with themselves in the city, and he is tied up so he could not escape. However, as the family is ready to sail away, they see Gray Wolf by the river, howling to Kazan, who immediately runs in her direction and leaves. The pair stays together, narrowly escaping a great forest fire, who ravages a vast part of the wilderness. Afterwards, they are captured by Henry Lottie, a trapper, and his companion, Paul Wayman, a former hunter and now an environmentalist and animal lover. It is likely that Wayman is the incarnation of the author, an ex-hunter and a nature lover himself. Led by his compassion for the two animals, Wayman buys them off from Lottie and frees them.
From there on, the couple goes to the north when they encounter a pack of dogs, having run away after their master died due to the smallpox epidemic, and Kazan once again becomes an alpha male after he fights and defeats their leader. However, led by their loneliness, the dogs soon after join the people at a hunting point, leaving Gray Wolf and Kazan in the wild.
The couple returns to their old lair, where once again Gray Wolf becomes a mother, of a single male cub, Baree. The half wolf, half dog pup quickly learns the laws of the wild and only after few months, ready to survive on his own, he leaves his parents. Afterwards, a large colony of beavers led by their alpha male Broken Tooth, settles down in the nearby river and starts building a bent, despite all efforts Kazan and his companion make to chase them away. One day Kazan accidentally kills his only ally against the intruders, a large river otter, after mistaking her for one of the beavers. Eventually the entire area around the couple's territory is flooded and they are forced to leave. They head north together until are separated by Sandy McTrigger, a gold digger and possible murderer. He captures Kazan with the plan to use him in fights. However, when Kazan and his opponent, half great dane, half mastiff known as Dane, face each other, they silently agree not to fight, thus earning the respect of an old man, Professor McGill, who buys off the two dogs from their owners. McGill and the dogs prepare for their journey to Fond Du Lac and soon leave. Several days later, Mctrigger, who apparently had tracked them down, tries to sneak on them, but is heard and attacked by Kazan. Using the opportunity, Kazan runs away just as McGill shoots Sandy multiple times, thus killing him.
The story continues with Joan and her husband, who have returned to the wild with their daughter. Soon after they see Kazan again away in the distance, who joins them for a moment, only to leave when he hears Gray Wolf howling for him. The book ends with the reunited pair who once again hunts together side by side under the moon.