Now that “Brokeback Mountain” has reinvigorated the cowboy genre, acclaimed “Don’t Come Knocking” (Sony Pictures Classics) director Wim Wenders turns his camera, as he did with his film “Paris, Texas,” to the American West. Shot mostly in Utah, Montana and Nevada, the film vividly captures the small towns of the West. However, it is hampered and eventually sinks under the weight of uncomfortable dialogue, a few subpar performances and its muddled, often inexplicable plot.

The film stars Sam Shepard (“Stealth”) as Howard Spence, a washed-up Western movie star whose dissolute lifestyle has begun to catch up with him. He abruptly leaves the set of his latest movie to go search for his roots, first visiting his mother (played by screen legend Eva Marie Saint), whom he has not seen in 30 years.

After learning that he may have a son by a woman he does not remember, Howard sets off to find him to determine if it’s true.

Howard finds Doreen (Jessica Lange, who last appeared in the similarly-themed “Broken Flowers”), who introduces him to their son, Earl (Gabriel Mann, “The Bourne Supremacy”). It is at this point that the movie falls apart. After meeting Howard, Earl screams at him, his girlfriend (Fairuza Balk, “Deuces Wild”) and anyone else who will listen, and throws all of his belongings out of his second-story window.

Mann and Balk have performed well in other movies, but they just don’t work in this one. The screenplay, written by Shepard, goes awry at this part of the film as well, throwing in long, meandering speeches that don’t ring true.

Other aspects of the film are similarly inauthentic, or just plain confusing. Saint’s character reacts to seeing her son for the first time in 30 years, and encountering an ominous detective inquiring about his whereabouts, in the same way that she does greeting the mailman.

Despite all of this, the film still has emotional resonance. Lange gives by far the best performance in the film, providing a perfect counterpoint to Shepard in their scenes together. Shepard is also effective at creating some sympathy for a largely unsympathetic character.

Ironically, while the film does not nearly reach the potential of its talented cast, Wenders proves his worth as a director. His direction transcends a myriad of other shortcomings to make “Don’t Come Knocking” a film that almost works.

“Don’t Come Knocking” opens in limited release on March 17.