Shadow is a wise, old golden retriever, who is very loyal and obedient to his owner, Peter, a teenage boy who loves him very dearly. Given his age, he sees the way of a dog as his own law. His pet comrades are Chance, a young, immature American bulldog, and Sassy, a Himalayan cat who respects Shadow despite him being a dog. He considers himself Chance's guardian as he feels he must watch over the "pup" and keep him from out of trouble. Chance thinks of him as an old fusspot and calls him "old timer", but still has respect for him as well. For an old dog, he can hold up on his own, as he is able to outrun a mountain lion and keep up in a fight against mean stray dogs.
- “Wake up and smell the kibble. They dumped us."
"No! It isn't true!"
"They love you and they dump you."
- ―Shadow telling Chance off for thinking the Seavers abandoned them
In the first movie, Homeward Bound: The Incredible Journey, after Shadow, Chance, and Sassy are left in the care of Kate, a family friend, when Kate leaves for a cattle drive with her horse, Shadow is suspicious of her departure. When Chance believes that the Seavers have abandoned them, Shadow defiantly refuses to believe that and decides to leave and return home to Peter. With little other choices, Chance and Sassy join him and depart to make their way through the treacherous wilderness of the Sierra Nevada mountain range to find their way home to the Seavers.
At one point, Sassy tries to cross a river rather than swim it with Chance and Shadow using some rocks and a rotted tree trunk, but the trunk breaks when she's halfway across and she's swept over a waterfall to her apparent death. Devastated by her presumed demise, Shadow and Chance continue on, heartbroken over losing her.
Later, Shadow and Chance are attacked by a ferocious mountain lion, but using a clever trick with some rocks set up like a seesaw, they are able to catapult the lion into the river with Shadow acting as the decoy to lure the lion into the trap. As they celebrate afterward, it is not long before they are reunited with Sassy, who survived going over the waterfall and was nursed back to health by a local hermit living in the mountains named Quentin.
As the reunited pets continue on through the woods, Chance tries to befriend a porcupine and gets punished when the porcupine swats him with its tail in annoyance, leaving several quills embedded in the side of Chance's muzzle. They later encounter a lost little girl named Molly, and Shadow, following a dog's natural loyalty to humans, convinces Chance and Sassy to stay with her overnight. The next morning, Shadow hears the search party of Molly's parents, U.S. Forest Rangers, and rescue team, and leads them back to Molly, reuniting her with her parents and getting medical attention. The Rangers recognize Shadow, Chance, and Sassy from some missing animal flyers that the Seavers had sent out when they learned of the pets disappearing from Kate's and take them to the local animal shelter to be picked up by the Seavers.
However, due to Chance's own past trauma with the dog pound, he believes the animal shelter is the pound and panics upon arrival. While Chance is taken to have the porcupine quills removed by the shelter's medical staff, Shadow is placed in one of the cages to await the Seavers. Sassy escaped and returns to free Shadow, and together, they free Chance from the medical room and escape back into the woods and resume heading home, unaware of the Seavers having been on their way to pick them up and reunite with them.
They soon reach the outskirts of San Francisco and have on the final obstacle to cross before reaching home: The local rail yard. After barely managing to avoid being run over by one of the Southern Pacific diesel locomotives as it passes through the yard with its train, Shadow, unfortunately, fails to see a large mud hole that had been boarded over, and the boards give way under his weight, sending him into the hole. Horrified, Chance and Sassy try to get him to climb out, but although he initially tries, despite the slippery, muddy slope, Shadow concedes defeat, considering himself too old to do it, and gives up. Refusing to abandon him when they are so close to their goal, Chance risks going down himself to try and encourage Shadow to try again, but Shadow seems dead set on just lying there and not even putting any effort into getting out. Chance is on the verge of heartbreak as he refuses to leave Shadow behind after everything they've been through already and Shadow being willing to give up when they were so close to reuniting with the Seavers.
However, his love for his boy is able to overcome Shadow's initial thoughts of surrender, and he is able to climb out and limp the rest of the way home to reunite with Peter only moments after Peter had thought Shadow couldn't make it after witnessing Chance and Sassy reunite with Jamie and Hope. With the family together again, things seemed to be going well now for the pets.
- “We're going to Canada, boy. And we're taking you with us."
"Go? I'd go anywhere with you, Peter.”
- ―Shadow happy to go on vacation to Canada with his boy
In the sequel, Homeward Bound II: Lost in San Francisco,
the Seavers are planning a trip up to Canada and are taking the pets with them. However, while Sassy and Shadow are more than happy to go with Hope and Peter, relations between Chance and Jamie have soured, with Chance only knowing he screwed up big time when Jamie angrily blames him for the family being late, getting to San Francisco International Airport to catch their flight due to his childish antics with Jamie and his baseball team at the park earlier making him loose the game, and disobeying his orders. Shadow remains pretty calm during the trip across the Golden Gate Bridge to the airport, but once inside and in their carriers to be placed in the plane's cargo hold, as they are being taken out to the plane, Chance mistakes the San Francisco International Airport for a dog pound and the airport workers for being dog pound workers and panics, Shadow says to Chance their human would never do that to us, knocking his carrier off to crack open being dragged between two baggage carts going in opposite directions, freeing him to go find Jamie and apologize to him. Sassy helps Shadow escape from his carrier after getting hers open, and they chase after Chance as he makes his way all the way back into the terminal to find Jamie before Shadow realizes the Seavers are probably back on the tarmac on their flight. As they try to locate the plane the Seavers are on, they spot airport security heading out to recover them so they can still make the flight themselves, and then head for the runway the plane is taxing towards to take off. Unfortunately, the plane lifts off and heads skywards, right before it would have run the animals over had it not been up to takeoff speed by then.
Separated from their owners again thanks to Chance and his paranoia about going back to the pound, after escaping from the airport and their security forces who were only trying to get the pets on the next flight to Canada to reunite them with the Seavers, the pets realize they are lost again and will have to find their way home once more. After Sassy tries to chew out Chance for his actions getting them into this predicament, Shadow remembers that they crossed the Golden Gate Bridge to get where they are now, so they have to cross it again to return to the house. With that, they depart and head into San Francisco to find the bridge. However, along the way, they end up running afoul of Ashcan and Pete, who are not too happy with Shadow and his pals crossing into their territory. Shadow tries to politely ask Ashcan to let them by, but when Pete goes after Sassy with the intent to eat her, Shadow turns vicious, warning Ashcan to back off, but Ashcan chooses to attack Shadow. When Riley and his gang show up, they quickly help force Ashcan and Pete of the scene, before Shadow realizes that Chance ran off to try and lure away what he thought was reinforcements for Ashcan and Pete. Riley sends Delilah to find Chance while he and the rest of his gang help Shadow and Sassy, helping them to hide from the "Blood Red Van" when it appears up the street and explaining that the van takes dogs to a lab for examination. Once it is gone, Shadow asks Riley for help getting back to the Golden Gate Bridge, but Riley refuses, leaving Shadow and Sassy to set off on their own.
Sometime later, Shadow and Sassy pass by a junkyard where Ashcan and Pete live and manage to avoid them when Pete keeps misunderstanding Ashcan's directions and lets them pass by unharmed, before noticing a house on fire, the same one that Sassy had tried to get food from earlier from the boy who lived there, Tucker, which had been set ablaze earlier by the discarded smoldering cigar from one of the "Blood Red Van" members, Jack. Hearing that Tucker is trapped inside as Tucker's parents plead with the San Francisco Fire Department battalion chief on the scene to send someone in to save him, Shadow braves the fire to sneak inside through the basement window to find Tucker and escort him out of the burning building. After Sassy follows to save Tucker's kitten Tiger, Tucker thanks Shadow for saving his life, and Riley, who had witnessed the entire event with his gang, agrees to allow Shadow and Sassy to stay with his gang until they find Chance.
When they return to Riley's hideout, they find Chance and Delilah there already. Shadow is furious with Chance for the concern and paranoia he caused to himself and Sassy, and Riley agrees that Chance and Delilah can't be together as Chance belongs to someone and not a stray like them. Refusing to accept the truth, Chance goes outside for some fresh air with Delilah, Shadow comes out to them and talks to Delilah, he tells her how Chance behaves at home and she won't be able to be there for him is something happens to Chance and they shouldn't be in love. Then the "Blood Red Van" enters the dockyard. While Delilah retreats into cover with Shadow, Sassy, Riley, and the others, Chance is unaware until Jack and Ralph confront him, where Jack lures Chance with a cheeseburger, allowing Ralph to snare him. Shadow, Riley, and the others are too late to save Chance initially, but after managing to get ahead of the van before it leaves the dockyard, on Sassy's suggestion, they form a roadblock to prevent the van from leaving. Upon seeing them, Jack tries to force Ralph into flat-out running them over instead of capturing them, but while Riley, Shadow, and the others scatter, Delilah stands her ground until she's nearly run over herself. Faking her paw being injured, she causes an enraged Bando to leap into the van and attack Jack and Ralph in retaliation, forcing them out of the van to be surrounded by Shadow and Riley's gang, who intimidate Jack and Ralph until the two try to flee, where Riley goes after Jack and Sledge go after Ralph, leaving Sassy to free Chance and the other captured dogs from the back of the van. While the freed dogs go after Jack and Ralph and trap them as they try to climb over a barbed-wire fence to escape the angry canines, Bando sets the "Blood Red Van" into reverse to roll off the dock and into the water to drown. Afterward, once Chance is told off by Bando for his actions and Delilah admits that Riley is right and she and Chance can't be together with a heartbroken Chance leaves. When Shadow tries to stop him, Chance tells him off for his and everyone else's actions, clearly angry with him and everyone else for trying to keep him and Deliah apart, saying he doesn't need Shadow, Sassy or anyone before he continues to depart.
Later, Riley told Shadow that he and his gang were unsuccessful in finding Chance. However, Riley decides that Shadow has more than proven that humans mean a lot to him and Sassy, and agrees to take them to the Golden Gate Bridge, with or without Chance. They reach the bridge by morning, and Riley sees Shadow and Sassy off as they depart to return home. As Shadow and Sassy head for the bridge, they stop in a construction yard as Shadow realizes he can't go home without Chance. Sassy realizes it as well, much to her own chagrin, and Shadow decides they have to go back and find him, only to be ambushed by Ashcan and Pete. Shadow again tells Ashcan to back off as he and Sassy are only trying to get home, but once more Ashcan and Shadow are forced to throw down as Pete corners Sassy. Luckily, Chance returns and manages to incapacitate Ashcan and Pete with a trick he pulled on Sassy earlier, and all three pets head for home, though Chance is still worried that Jamie is still furious with him.
Once across the Golden Gate Bridge, the pets just have to cross one more road and hill to reach the house, but while Shadow and Sassy get across no problem, Chance stops midway across the road to look back at San Francisco, thinking about Delilah. Shadow realizes Chance needs time to get over his broken heart, but soon hears the rumble of an approaching semi-truck, and when Sassy has visual confirmation of it, Shadow barks to Chance to look out as the truck is bearing down on him. Unknown to the pets, the Seavers were in their SUV behind the truck, and barely avoid hitting the back of it when it starts to jack-knife on the rain-slick road to try and avoid Chance.
After Bob and Laura make sure the kids are alright, they prepare to get out to speak to the truck driver when Peter sees Shadow and Sassy coming down the hill to check on Chance. Upon when Peter and Hope see them, Bob and Laura are amazed the pets found their way home again and happily reunite with them. However, as Jamie calls out to Chance, Shadow and Sassy fear the worst for Chance, but thankfully, Chance saw the truck in time and cowered in fear, thereby avoiding being injured and reuniting with an apologetic Jamie.
Sometime later, the family is back home, but Chance is still down in the dumps about Delilah until she appears at the entrance to the driveway. Upon Riley's encouragement to follow her heart, Delilah decided to leave Riley's gang and join Chance. When Shadow and Sassy see her, they are amazed she came all this way to be with Chance again, and Bob agrees that Delilah can stay, much to Chance's happiness.