A boy and his father travel a long distance from their home to release a fox into the forest. The boy, whose name is Peter, found the little fox when it was just a kit, grown attached to it and called it Pax. He clearly doesn’t want to leave the fox behind, but succumbs to his father’s pressure, throws Pax’s favorite toy soldier into the forest and gets into the car to leave. It is further revealed that the father is about to go into the war, and he leaves the boy with his grandfather. At his grandfather’s, Peter suddenly has a rush of anxiety and realizes that it was a big mistake to leave Pax behind. He packs his bag, looks at the map to check where he left Pax, and leaves home to bring his fox back.
Meanwhile, Pax is determined to wait for his boy at the same spot he left him. He suddenly discovers that he’s not alone. A female fox joins him, and she berates him for the human smell on him. The female fox, called Bristle, experienced human cruelty and swore to never trust them again. Bristle is accompanied by a smaller fox, her brother called Runt. Runt is eager to be friends with Pax, while Bristle is reluctant. They bring Pax into their hiding place to spend the night with them.
On his path to retrieve Pax, Peter is faced with the threats of other people, who will report him as a runaway if not careful. He spends some time hiding on a school playground and manages to escape. He finds himself on a secluded farm and, while following the map directions for a shortcut, falls down and breaks his leg.
Far away from Peter, Pax is determined to reunite with his boy. An old gray fox, a pack leader, decides to accompany him south. Gray informs Pax that there is a war coming to their lands. Pax and Gray get attacked by a coyote, and Gray gets severely injured. After Gray dies, Pax returns to his pack to inform them of his death.
Peter wakes up in someone’s barn. He meets the owner, a woman called Vola. She helps him with his broken leg. Peter notices that Vola is missing her leg, and she tells him that she lost it in the war. He wants to immediately continue his search, but his leg doesn’t allow him to. He asks Vola for help, and she agrees.
Pax goes back to the south, secretly followed by Bristle and Runt. He comes across a war camp, and discovers Peter’s father there. Runt gets injured in an explosion near the war camp and loses one of his paws. Unable to return, Pax, Bristle and Runt stay nearby the camp.
Peter and Vola slowly become friends as the time goes by. She reveals to him that she killed a man in war, and was hunted by it ever since. Peter is determined to help Vola return to the human world, he performs a play with her wood puppets that shows her rising from the ashes like a phoenix. Vola is angry at him at first, but then she accepts his conditions to break her isolation before he continues his search for Pax. She helps him by asking her friend bus driver to drive him as close to the place where he left Pax as possible.
Meanwhile, Pax and his two foxes get attacked by a group of coyotes, who sensed Runt’s injury. While battling the coyotes, Pax believes to hear his boy calling him. He sees the boy’s father talking to and hugging a boy similar to Peter, but not quite like his boy, which confuses him.
Finally, Pax and Peter reunite, and Peter helps them fight off the coyotes. After seeing the other two foxes, Peter realizes that Pax found his place, that he now belongs to them, and throws Pax’s favorite toy soldier into the forest once again.
