The film is narrated by the character of Chance. Chance starts his story by giving the audience a brief history of his life. He was abandoned when he was young and left to live on the streets. This eventually put him behind bars but a family rescued him by adopting him and giving him his name. But Chance points out that it's their home, not his...he doesn't need anybody.

Chance does admit that their home is great. "Lots of space, fresh air, plenty of interesting things to explore, and all the underwear I can eat." This is, of course, when the audience realizes that Chance is a dog; an American Bull Dog. To be even more specific, an American Bulldog that likes to eat underwear.

As Chance shreds some of these aforementioned articles of clothing, he wakes Sassy, a Himalayan cat. She complains that, "even a very great beauty needs her beauty sleep." In the voice-over, Chance explains that there are more clothes to be shredded because Bob is marrying Laura. Her daughter, Hope, belongs to Sassy. Jamie, the youngest of Laura's children, belongs to Chance. Although Chance admits that Jamie has some very good ideas, Chance says he doesn't need him. Laura's oldest boy, Peter, belongs to Shadow, an older Golden Retriever. "Shadow was faithful. Shadow was loyal. Shadow was a chump."

Back in the house, Sassy and Chance have a sparring of words and Sassy finally pushes the wrong buttons with her 'flat-faced, butt sniffer' comment and the chase is on. Outside, the wedding proceedings end to the sounds of household items crashing and cat screeches.

At the reception, Chance tries to get food anyway he can-begging, looking pitiful, bargaining, etc. All he ends up getting is some "green stuff", which he promptly spits out.

As Chance is wandering, desperately looking for a handout, a wedding guest and Laura's mother discuss what is going to happen to the animals while the family is in San Francisco. Laura's mother explains that a good friend of Laura and Bob is going to keep them on her farm until the family comes home.

Meanwhile, Sassy berates Chance's begging skills. Chance dares her to do better. She proves her theory that she can get food by pretending she doesn't want food, getting two pieces of shrimp, also proving that "Cats Rule and Dogs Drool."

Outside, Peter and Shadow are playing basketball. Peter, obviously sad about leaving Shadow, hugs him tight. Chance looks on, muttering, "I hate this mushy stuff" and runs off to find more food. Bob comes to talk to Peter and it's obvious that Peter doesn't understand why they can't take the animals to San Francisco with them, even after Bob explains there wouldn't be enough room for them. Peter is also afraid Shadow will think he's being abandoned. Bob assures him he'll have a great time at the farm, but Peter is unimpressed.

Chance is busy stalking the cake, using Sassy's techniques. They work, to everyone's chagrin. Chance dives right into the middle of the cake, inviting everyone to dig in.

After the reception, Laura and Bob are packing up the car as Chance invents the catapult, using the teeter totter, Sassy and the big litter box. Chance also learns that cake and polyester don't mix after he spits up his lunch. Meanwhile, Shadow wonders about the luggage. Chance admits that he likes to do things with the family and that he's starting to believe that things are going to be better.

The family loads up into the car and take off. The next day they arrive at Kate's ranch. Chance barrels his way out and immediately begins sniffing around. Peter eyes Kate over, trying to decide if she's suited to take care of the pets. She assures them the animals will be fine despite the fact that she'll be gone a couple of days to drive the horses to winter grazing. She tells them that her friend Frank will be around to take care of everything. The kids say good-bye to their pets. Peter hugs Shadow and tells him to stay. Shadow watches Peter drive away, obviously wanting to run after him, but not letting himself disobey the stay command. (If you have any sentimentality at all, this moment is a bit tear-jerkish)

Life goes on. Chance takes advantage of the new surroundings, exploring everything. He fears nothing, except for Birdzilla, a large turkey. Back at the house, Shadow is still moping. Chance advises him to stop waiting, that humans love you then dump you. Shadow lectures him on the finer points of being a dog. Chance apologizes, but is still unconvinced that humans are worth the bother.

Days later, Kate gets ready to leave, leaving a note for Frank. One of the pages floats away as she leaves the barn. The animals don't understand why Kate is leaving and Shadow gets nervous, knowing Peter should have been back by now. Chance starts to feel trapped and it reminds him of the pound-the place where you go when humans don't want you anymore. Shadow doesn't believe Chance about the pound and Sassy refuses to believe that anyone wouldn't want her.

Shadow finally makes the decision to go home, worried that something is wrong with Peter. Sassy follows him, asking if he really knows what he's doing. Chance defiantly states that he's staying right there on the farm. However, Birdzilla returns and Chance follows Shadow and Sassy. (A nifty little ad-lib spot to look for: after Chance jumps over the fence, he runs through some chickens, yelling "Look out chicken butts!" He looks over his shoulder and says, "Pardon me.")

Shadow thinks that home is over the next hill and that they'll be home before dark. Sassy argues that it took them days to get to the farm. Shadow says that they're taking the short cut: straight up and over. Chance catches up and tells him that he's coming along to protect them.

"And so began the most perilous journey of our lives."

Peter is in class, doodling pictures of Shadow. The teacher is giving a lecture on the Sierra Mountains: They extend over 250 miles North and South and are 50 miles East and West, making them the 2nd largest mountain range in the western United States. Of course, these are the mountains that the pets are heading into.

Sassy is already complaining and Chance is starting to get tired. Shadow is fine.

Back at the farm Frank arrives and finds Kate's note. (Remember, half of it floated away). He misunderstands and thinks that Kate took the pets with her on the drive. He's incredulous but gets to work.

The pets have reached the top of the hill. They look out only to see the mountains. Chance is in awe and says, "You can see everything up here-except the house, I don't see the house, where's the house, Shadow?" Sassy's a bit peeved but Shadow becomes more determined to get home. Chance tells him that this couldn't possibly be the way home, but Shadow tells him that he has a 6th sense about these things and that Chance will even have it someday. Sassy argues that Shadow isn't as young as he used to be. Nothing can deter Shadow and the others eventually follow him. In the voice-over, Chance says that he admires Shadow's faith and courage.

Insert nice traveling montage

Shadow warns Chance to pace himself, but of course he doesn't listen and that night he's "too pooped to poop." As they try to sleep, they hear animal noises and Chance gets scared. Shadow tells them that it's probably a moose. Chance says, "Oh. What's a moose?" (A bit of irony here, since the last time I checked, the moose was reportedly Michael J. Fox's favorite animal.) Shadow tells them that a moose is a big razor-toothed animal that comes out at night to eat the tails off of smaller animals. They can even reach to the top of trees. The pets sleep uneasily.

The next morning, Shadow informs Chance and Sassy that he's found breakfast. Sassy complains that it can't be any good if a dog thinks it's good. Chance tells her to stay there and diet. Sassy asks if he's calling her fat. He says of course not, for a hippopotamus. At this moment, Chance runs head on into a small tree and says, "I meant to do that." Sassy tells him he deserved it.

Breakfast is fish, but Chance can't catch any. He asks Shadow how he got his and Shadow tells him, "Sassy." Chance doesn't want to but finally asks Sassy to catch him a fish. She forces him to say "Cats rule and dogs drool." Sassy gets him a fish, but as Chance tries to catch the fish as it flops on the bank, he comes upon some bear cubs who try to steal the fish. He shoos them away, but the mother bear comes back and shoos away the pets.

They come upon a river and Shadow decides that they're going to have to cross it. As they wait for Shadow, Sassy lectures Chance on his run in with the bears. Chance's only response is, "Oh, go hawk up a hairball."

Shadow returns and tells them that they have to cross the river. The dogs swim over but Sassy refuses, even though the current's gentle. She goes downstream determined to find a dry way across. She finds one but as she crosses, a log rolls and she falls in the river. The current's stronger here and despite Shadow's rescue attempt, Sassy goes over the waterfall.

The dogs stay the night at the waterfall. Shadow blames himself for losing Sassy because it's his responsibility to love and protect her, Chance and Peter. He tells Chance it's his responsibility to love and protect Jamie. Chance protests that they didn't ask for the job, but Shadow tells him it's been this way since the first wild dogs took it upon themselves to watch over man. In the voice-over, Chance says that Shadow seemed wise and ancient and that he hoped that one day he'd be like him. The next day, Shadow says good-bye to Sassy at the waterfall, and the dogs move on.

Downstream, a birdwatcher finds Sassy and is amazed that she's still alive, albeit barely. He lives in the mountains and takes her home to take care of her.

Chance and Shadow try to catch food but Chance is too impatient and too loud. Shadow gives up on him. They try to fish, but all Chance catches is a crawfish.

Meanwhile, back at the farm, Kate returns. She and Frank quickly realize that the pets are missing. Kate calls all the authorities. The park ranger tells her that he doubts they'll survive because of the bears and mountain lions. Kate calls the family and the kids are heartbroken. Peter blames Bob for their disappearance and storms away to his room. The next day, Bob makes up a missing poster and has it sent everywhere.

At the birdwatcher's cabin, Sassy awakens. The man gives her some goat's milk. As she drinks, Sassy asks, "Was that my 6th life? Oh, I'll just say it was my 4th."

Shadow and Chance are still traveling, thinking of food constantly. A mountain lion begins to stalk them. Chance spots the mountain lion while Shadow is fishing. Shadow doesn't believe him at first, but finally does when the mountain lion screams at them. They begin running. Chance berates himself for running from a cat. "But this isn't your ordinary housecat. This is like Arnold Schwarzakitty." The dogs come upon a cliff and find themselves trapped. Chance, in a panic, starts telling Shadow where he's buried everything and mentions the seesaw. Shadow looks around himself and tells Chance, "You're a genius!" Chance's answer is, "I am not!...What's a genius?"

The dogs team up and trick the cat onto a rock balanced like a see saw. Chance does his catapult trick and throws the mountain lion over the cliff yelling down at him, "Dogs rule and cats drool!"

Back at the cabin, Sassy hears the dogs cheering barks and runs off to find them. The pets are gleefully reunited. (Another one of those nifty little ad-libs: Chance trips and says, "Oops, gopher hole").

With Sassy back, the pets eat well. The pets start imagining how the family will react when they get home and Chance admits that he's eager to see Jamie.

Chance, ever curious, starts following a porcupine. Shadow warns him off, but Chance is determined to sniff this strange creature out. However, the porcupine smacks Chance in the snout. "He bit me with his butt!" Sassy tries to remove the quills from Chance's snout but can't.

We cut from a shot of the porcupine walking away, to the San Francisco police department where a mohawked criminal is being dragged away. Peter tries to report the missing pets, but the cop tells him they don't have time to look for them. The cop suggests making up reward posters. Back at home, Peter finds the posters that Bob has already sent out.

The quills are beginning to make Chance sick. They come upon another river and Sassy seems more willing to swim across, trying to figure out how to get Chance across. However, before they can even start, they hear some whimpers. Shadow finds a lost little girl. The pets stay the night with her, making her feel safer. The girl's parents and some park rangers are heard the next morning calling out her name (Molly). Shadow barks them over and the family is reunited. The rangers recognize the pets from Bob's missing-pet posters. Chance is leery of the rangers and their uniforms, but Shadow convinces him that they only want to help.

The ranger calls Bob and tells him that the pets have been found and that they're being taken to the Pineville Animal Shelter. He's ecstatic and he and Laura round up the kids to go pick up the pets. As all this is going on, we can tell from the surroundings that it's Halloween.

When Chance sees that they're being taken to the pound, he freaks out. A muzzle is put on him and Shadow believes Chance's stories about the pound being evil. He tells Sassy to run. She escapes and watches as Chance and Shadow are taken in. Chance is taken to the back room and is convinced he'll never come out again.

Chance is taken to the back room so that a vet can remove the porcupine quills. Chance thinks that they're torturing him.

Begin "Mission Impossible" theme: Sassy, determined not to lose her pals again, breaks into the shelter to spring her buddies.

Back in the operating room, Chance starts confessing to everything he's ever done wrong.

Back in the kennels, Sassy receives catcalls from the dogs there. She finds Shadow and releases him from his cage. They find the back room and hear Chance yelling and believe that he's being killed. Sassy distracts 'fat boy' while Shadow 'rescues' Chance.

Fortunately, all the quills have been removed. Chance and Shadow run out. Sassy is caught, but dropped as the dogs run right into 'fat boy.' The pets run out of the shelter and Sassy and Shadow slip under the fence. Chance is caught in the fence by his collar and 'fat boy' (I never caught his name) grabs him. Shadow scares him and Chance finally slips under the fence. They run off as the Shelter workers watch, helpless to catch them.

The family is on their way. They drive past the pets going the other way, but neither group notices the other. However, Shadow stops and senses that they should go back. This time he ignores his instincts and they go on. As they do, Chance realizes that Shadow and Sassy risked their lives for him.

The family is understandably upset, but Bob is inspired by Peter's determination and vows not to give up.

The pets finally reach their town, rejoicing. However, while crossing the trainyard, Shadows falls into a deep, muddy hole, breaking his front leg. He tries to crawl out but can't crawl up the slippery side. He tells Chance and Sassy to go on, that he can't make it. Chance jumps in the hole and tells him that Shadow taught him not to give up and that he won't let Shadow give up now. Shadow tells him that he knows all that he needs but now he must learn to say good-bye. The scene ends with Chance telling Shadow that he won't let him give up.

It's Thanksgiving (or is it Christmas? It's sort of ambiguous)and the family's back home. Laura tells her mother that the kids are better now that they're home, but from her tone one can tell that they still miss their pets. Outside, Bob is playing basketball with the kids who start calling him 'Dad,' even Peter.

Jamie is the first to hear the dog bark. He starts calling Chance's name and the family waits, breathless. And here he comes! Running full speed over the hill yelling for Jamie. He knocks the poor kid over, so happy to be home. Sassy is next and Hope scoops her up, squeezing her.

But where's Shadow? The family waits, but Peter rationalizes that Shadow was too old to make it the entire way. But here he comes, limping, but alive and well. When he sees Peter he moves faster until he's running.

"It was Shadow's victory, really. His belief was the thing that got us through. And in that moment I saw the years lift from him. He was a puppy again, reunited with his best friend. As we turned to go inside the house, a strange new feeling came over me. I had a family. And I had found out that sacrifice and friendship and even love were more than just the mushy stuff. At last, for the first time in my life-I was home......Turkey!!!!"