In John Sayles' universe, you are what you speak. His movies are filled with tavern talk, monologues bred by a culture that sits at a bar staring straight ahead at nothing, or a mirror. And it is the talk of these peerless spielers, spinning out their tastes and obsessions, rattling on about Polynesian leper colonies, Ernie Banks, shirts with epaulets and chocolate pudding that makes his "The Brother From Another Planet," for all its flaws, a joy, not to watch, but to listen to.

"Brother" is a cheaply made science fiction film that Sayles wrote, produced and shot in a little over a month. When an alien fugitive (Joe Morton) lands in New York, he ends up in Harlem; he looks like an ordinary black man (except for the hooked claws growing from his three-toed feet), so he blends right in. When the habitue's of a neighborhood hooch joint ask him his name, he doesn't respond (he's mute), so they simply call him "Brother." "Man is deaf, man is crazy, or man is a wino," says one of the regulars. When the Brother refuses a shot of whiskey, the regular is satisfied. "Man is crazy," he says contentedly.

The Brother is pursued by two extraterrestrial bounty hunters (played with a stylish mix of Devo and the Keystone Kops by Sayles himself and David Strathairn). They're white, so they don't blend in; everyone from the barflies to the welfare bureaucracy conspires to stymie them. The chief defensive weapon: the spiel.

Sayles is no storyteller; despite the verve of its language, "The Brother From Another Planet" eventually sags of its own weight. And all his movies are hampered by an almost shocking ignorance of filmmaking fundamentals -- he just doesn't know where to put his camera. The movie would have benefited from more attention to the bounty hunters, whose difficulties with Harlem culture would have balanced the Brother's strange ease of assimilation. Instead, the plot takes a centrifugal turn as the Brother roots out a scag baron whose drugs are poisoning the community.

Joe Morton plays the Brother with a sweet, pantomimed grace; an innocent impervious to the cynical talk that whirls around him, he's the perfect counterpoint to the movie's elaborate, sometimes stagy gab. When people ask him where he's from, he points up with his thumb, and they ask "Uptown?"; and when people offer their hands for a slap, he lays his palm upward alongside -- he's the stranger in a strange land.

The Brother's reactions are Sayles' way of making the world seem new again. When the Brother rides the subway, a magician (the scene-stealing Fisher Stevens) performs a card trick, then says, "I got another trick for you -- wanna see all the white people disappear?"; and, as the train reaches the last stop before Harlem, that's just what happens. There's satire here, but it also epitomizes what's best about "The Brother From Another Planet," the way it has of investing the mundane with magic. It's an "E.T." for adults. "The Brother From Another Planet," opening today at the Key Theater, is rated PG.