"Up," the latest animation triumph from Disney/Pixar, begins with a deeply moving love story, told in a sequence of mostly silent images. It's about Carl and Ellie, who meet as children and share a dream of adventure. They grow up and marry but somehow life's tribulations, both mundane and profound, keep thwarting their plans to explore the world.

Then Ellie dies, leaving behind a lonely widower of 78. Angry at faceless developers whose high-rise buildings threaten the couple's quaint lifelong home, Carl finally takes off -- literally -- on the adventure he and Ellie never had. He inflates enough helium balloons to lift his house off the ground and sets sail for legendary Paradise Falls in South America.

Carl soon discovers an accidental stowaway. Eight-year-old Russell, who had been begging Carl to help him win an "Assisting the Elderly" badge in a Boy Scout knockoff group called the Wilderness Explorers, was on the front porch of the house when it lifted off and had no choice but to hang on for dear life.

The second act of "Up" is devoted to their adventures in and over South America. Along with Carl and Russell and the ever-present house to which they are tethered, look for a large and lovable bird, a long-lost explorer and the pack of talking dogs that he commands. The dogs' occasional ferocity probably is responsible for "Up's" PG rating, which is rare in mainstream animation.

While a bit formulaic -- think Indiana Jones in animation -- this section is nonetheless imaginative and funny.

It also gradually bonds the lonely old man who needs a companion and the young boy who needs a positive male influence in his life. That theme is further developed as the movie winds to its happy conclusion.

Credits are due to Pixar vet Pete Docter for his direction and for writing the screenplay along with Bob Peterson and Tom McCarthy. Peterson also served as co-director.

The principal characters are effectively voiced by Edward Asner (Carl), Jordan Nagai (Russell) and Christopher Plummer (long-lost explorer Charles Muntz).

If a construction supervisor's brief appearance causes a where-have-I-heard-that-guy-before moment, it's probably because the voice belongs to John Ratzenberger of the old "Cheers" TV series (he was the hapless mailman).

Some theaters are offering "Up" in 3-D, but it's hard to believe it could improve on the vivid 2-D version. Either way, "Up" can take a place among the best Pixar movies.

The poignant opening sequence alone is worth the price of admission, especially if there's someone in your life whom you can't imagine living without.