SPOILERS ALERT
Homeward Bound: The Incredible Journey is an important film from my life because it's the first film I remember seeing in the cinema of my home town as a 4-year old scamp. The story is based on the Sheila Burnford novel, and is a reason why it's not possible to write this one off as a brainless Lassie clone.
The basic story: Two dogs and a cat happily live in the Seaver family when the new husband to the mother of the three children, gets a job in the city and they have to temporarily move into inner San Francisco while the animals are sent to a ranch to live for a couple of months. The bonds between the animals and the children they watch out for are especially strong, and Shadow the golden retriever and Sassy the Himalayan cat are heartbroken as the children are, though the young and happy-go-lucky American Bulldog known as Chance is a little less concerned and somewhat cynical (due in part to his voice-over explaining his being abandoned as a pup, picked up to an animal shelter, and being bought by the family), though his growth as a character during the story provides much of the important storytelling.
The three pets escape the ranch and head off into the wide and dangerous wilderness (fantastic wilderness settings by the way), driven on by Shadow's instincts of direction. They meet several perils along the way, hoping to make it home, while the family and the ranch hosts are suddenly concerned about the animal disappearance. There are funny moments all the way through, great dialogue between the three animals and hilarious lines (see - memorable quotes), and a touching comradeship that grows between the main characters during the course of the storytelling, punctuated by moments of sadness (such as when Sassy's arrogance of trying to cross a river without getting wet causes her to fall in the river and get washed down a waterfall, leaves a moment of loss that is felt deeply by the viewers).
Somehow though, I fail to see what the inclusion of saving the girl lost in the wilderness adds to the story and the journey they take. Somehow, it seems a little unnecessary as part of the story.
The ending cranks the stakes higher when shadow falls into a pit in a trainyard and having hurt his leg, finds it hard to get out and gives up, exhausted, followed by Chance climbing in with him to persuade him to climb out, telling him how important he is to him and how he's pushed them this far so he shouldn't throw it all away so easily.
The way that this scene (brilliantly done) isn't concluded leaves an ambiguity that carries on into the final scene when Chance and Sassy return home, but Shadow is nowhere to be seen. Then just as all seems lost, he slowly appears, and is reunited with the family. Chance's conclusion at the end speaks of the comradeship that has developed between he and his fellows on the journey, and the realisation to what home really is from his long journey to get there, leaves a fine epilogue to demonstrate how much his character has grown, but also how the other two have as well. Hang on a second, I think I'm going to cry...
Anyway, I haven't read Sheila Burnford's book, so I don't pretend to know where the differences between book and film lie. But this is a film that all the family can watch, and while the tots will love the talking animals, older viewers will understand the plot line better (as I found when I watched the film again after several years without seeing it). This film is a masterpiece in cinema, and I suggest that if you haven't seen it you go out and get it!
And please avoid the sequel (see my review for Homeward Bound II!)

They changed the title of this atrocity to An Unexpected Love. The only thing worse is the film itself. The script contains dialogue that would be laughed out of a third grade play recital. At one point when the wife leaves the husband, a bad cover of All by Myself plays over the soundtrack! No kidding. The actors try but are defeated by the inept, unbelievably terrible script. Direction is staggeringly bad. No wonder Lifetime has such a bad reputation. How do things like this get made. I'm turning off the television before it's over!