Pixar movies are beautiful to look at, but what takes your breath away is the story. They don’t rely on fairy tales or best-selling books with pre-sold stories and characters we are already attached to. And, as if challenging themselves to make it even harder, they take on increasingly unlikely protagonists — a gourmet rat, an almost-wordless robot, and now a cranky old man, and somehow they make us fall in love with them.

In some ways, this is the oldest and most enduring of tales, the story of a journey. And this is one that started a long time ago. A brief prologue introduces us to Carl and Ellie, a boy and girl who dream of adventure. They pledge to follow their hero, explorer Charles Muntz, to see Paradise Falls in South America.

Then they grow up and get married and life intervenes. He sells balloons and she works with birds. They save for their trip but keep having to use the money for un-adventuresome expenses like repairing the roof. Then Ellie dies, and Carl (voice of Ed Asner) is left alone. Developers are closing in on his little house. He just can’t bear to lose anything more. And so he takes the one thing he has and the one thing he knows and ties so many balloons to his house that it lifts, yes, up into the sky, so he can follow Muntz to Paradise Falls at last.

But he does not realize he has an inadvertent stowaway. Russell (voice of Jordan Nagai), a pudgy, trusting, and irrepressibly cheerful little Wilderness Adventure scout who needs to assist an elderly person so that he can get a badge. They arrive in South America and as they pull the house, still aloft, toward Paradise Falls, they meet an exotic bird, talking dogs, and several kinds of danger, and have to rethink some of what they thought they knew and some of what they thought was most important to them.

The visuals are splendid, making subtle but powerful use of the 3D technology to make some scenes feel spacious and some claustrophobic. Carl and his world are all rectangles, Russell all curves. The Tabletop Mountains-inspired landscapes are stunning and the balloons are buoyant marvels, thousands of them, each moving separately but affecting all of the others, the shiny crayon dots of pure color amid the dusty rock and the earth tones of Carl’s wrinkles, gray hair, and old clothes. The other glowing colors on screen are the iridescent feathers of the bird, inspired by the monal pheasant.

There are a couple of logical and chronological inconsistencies that are distracting. But the dogs, with special collars that allow them to give voice to the canine purity of their feelings, are utterly charming — and there is a clever twist to keep the scariest one from being too scary. Another pleasure of the film comes from the way the precision of the graphic design is matched by some welcome and very human messiness in the story. Everything is not resolved too neatly but everything is resolved with a tenderness and spirit that is like helium for the heart.