A Canadian family in Ontario named Hunter has decided to go on a trip to England so that the patriarch, James, can accept a temporary position. While away, the three beloved pets of the family are left in the care of a close family friend named John Longridge. The pets are Bodger, an aging bull terrier, Bodger's boon companion Tao, a Siamese cat, and the latest addition to the menagerie, Luath, a golden Labrador. Longridge decides to go on a two-day hunting trip by canoe and arrange for his neighbors, the Oakes, to care for the pets while away.
Longridge writes a letter to the Oakes explaining how he will be dropping the animals off at their place the next day after taking them for a walk before he sets off for an expedition. Overnight, Tao accidentally causes the pages to fall into the fireplace where everything is burned except for Longridge's signature. When Mrs. Oakes comes across this remnant while Longridge is walking the dogs, she assumes that he took the pets with him on his hunting trip.
When Longridge leaves, the animals decide to head off on their incredible journey in order to track their way back to their owners, the Hunters. Since Bodger is deaf in his left ear, Luath remains a near-constant companion on that side while the curious cat generally trails behind. The journey will take them across a vast expanse of Canadian wilderness which will test the limits of their domesticity and force them to rely upon their untamed instinctual behaviors in order to survive.
One of their many encounters with wild animals more at home in the wilderness is a bear cub that tries to attack Bodger only to come face to face with the ferocity of a cat willing to do anything to protect its closest companion. Once the much younger Luath arrives on the scene, the ursine threat is taken away by its mother.
Curiosity nearly kills the cat when Tao is knocked out after a beaver dam collapse while trying to make it across a river. It is only through the intervention of a young girl named Heidi that the cat survives, but at the cost of deafness for three days on account of water filling the feline's ears. Heidi and her family are able to gently tend to Tao's injuries long enough for the cat to regain his ability to hear before he sets off to find his two canine buddies and complete the journey.
Once reunited, the three animals come up to a frail old man with cognitive disabilities reaching the point that he confuses the dogs and cat with being human beings. Later, Luath crosses paths with a porcupine and he makes the mistake of hunting for food. The quills which lodge into his face become infected and are eventually taken out and treated by a kindly old couple named Mackenzie. They also take in Bodger, recognizing that despite his feral appearance, he is clearly a beloved pet who has gotten lost in the wild. The kind-hearted husband and wife are dedicated to adopting the dogs as their own, but Tao furtively unlocks the barn where they have been comfortably kept so that the three can resume their journey back to the Hunter family.
Stories of the indomitable trio make their back to Longridge and the Oakes and they figure out the purpose and final destination. They also realize that the animals are headed toward a treacherous pass just as winter is approaching. Longridge contacts the Hunters to tell them of these events and only cat love Elizabeth holds out hope that each of the pets will survive and make it back to them. The family joins Longridge on a trip to their summer cottage and even a reluctant Elizabeth agrees to go after it is pointed out that the cottage lies firmly within the route that the animals are deemed to be taking.
On Peter Hunter's birthday, while walking in the forest, the sound of a dog barking is heard in the distance which sounds like that of Luath. Suddenly, Tao is seen running full speed toward them and Elizabeth picks the cat up in a tight, loving hug. The cat is followed by the golden Lab who jumps into the waiting arms of her father, James. Bodger, however, is absent and Peter grows more despondent as he sets off to try to find him. Longridge joins the boy and soon Peter receives the greatest birthday present has ever or will ever receive as the old bull terrier slowly and lovingly greets him.
