Dora is a retired schoolteacher who supplements her pension by writing letters for Rio de Janeiro's poor and illiterate. Some of the letters she tears up without ever mailing; others she puts in a drawer in her apartment, where they yellow and become offbeat mementos of other people's lives. One of those letters, however, seems to have a life of its own, or at least a will to live that Dora can't subdue.

It belongs to a woman who died shortly after dictating it, and it concerns her young son, Josue, and his desire to see his father, who took off years ago for the Brazilian outback. And when Josue -- now a street urchin who sleeps not far from Dora's writing stand in Rio's Central Station -- discovers the letter has never been mailed, it triggers a two-tiered, many-teared odyssey through the heart of one of the world's most desolate regions.

What makes award-winning director Walter Salles' odyssey so different from other road films is that it involves two characters who aren't particularly likable, either to the viewers or to one another. Dora (Fernanda Montenegro) calls young Josue (Vinicius de Oliveira) "a brat." She's being kind, really. But Josue knows the truth about Dora; for years she's been charging poor people for a service she doesn't perform. In fact, Dora and her best friend, Irene (Marilian Petra), read the letters for their own amusement and make harsh judgments about both the senders and the intended recipients.

Why Dora decides to extend herself to this boy and deliver him to a father she's convinced is -- like her own -- a drunkard who abandoned his family is something that becomes apparent only when Dora and Josue leave the bustling comfort of the Central Station for the human wilderness beyond.

But Salles' film is more than a personal tale of two lost souls each seeking fathers. It's a nerve-shattering portrait of a land where petty thievery can lead to summary execution and children are sold for $2,000 a head to unscrupulous entrepreneurs.

Adding to the agita is the dusty brown cinematography that captures both the sooty sameness of life in Rio's slums and the harsh reality of the windblown desert beyond. And like all good road pictures -- from Easy Rider to Finding Graceland -- Central Station is thick with metaphor; taxis and buses take on a meaning all their own. It's a film you have to pay close attention to.

Not everything Salle tries works. The film is very talky, which means English-language audiences have to read fast. And at times it seems ready to slip into road-film cliches. Yet time and again Salles reinvents his film before your very eyes, leaving you with a sense of surprise and wonder that only a very personal film can aim for.

Central Station has won more awards worldwide than most films have assistant producers. But in the end, it's much more than a movie: it's a love letter to the fatherless children of the world. A letter that, fortunately for us, got posted. And delivered.