No genre has as much baggage as a Western: The label instantly conjures a set of narrow thematic and narrative formulas. After all, when was the last time a director set a movie in the wild Western frontier just because he liked the outfits? The utterly peculiar character of that place and time is too potent to be ignored. The rugged individualism, easy violence and rough justice of the age beg for satisfying if predictable stories. “Appaloosa,” on the other hand, has a refreshingly new saga to tell for a Western — a story of deep and abiding affection between two friends.

Not that you’d know that’s what you were watching until the last half hour of the film.

His attentions divided between serving both as a director and lead actor, Ed Harris allows the heart of his story to be smothered with a bevy of promising but ultimately anticlimactic plot lines. There’s the confrontation between the evil Rousseauian rancher and the law, an exposed love triangle and several showdowns between our protagonists and hordes of enemies, but few of these arcs are pursued with much vigor beyond the considerable suspense of their introduction. As surprisingly enjoyable as this overabundance of plot lines is, they leave the audience uncertain of what exactly the movie is about.

Terrorized by a lawless rancher (Jeremy Irons) and his cronies, the aldermen of the town of Appaloosa ask wandering super-lawmen-for-hire Vergil Cole (Ed Harris) and Everett Hitch (Viggo Mortensen) to take back control of their town, setting up what initially appears to be the film’s central drama. The confrontations between Harris and Irons are thoroughly satisfying, especially when Harris dials up the clipped menace in his icy blue eyes and gaunt visage. Irons delivers a less enthralling performance. Flipping predictably between confident charm and murderous rage, Irons’s rancher is more impotent than threatening.

This tale of law and order is swiftly sidelined by the arrival of a particularly homely looking Renee Zellweger. With a scrunched and ruddy face, Zellweger seems an unlikely candidate for Harris’s adoration, but Cole falls like a giggling schoolboy, revealing a fascinating immaturity behind his gunman’s confidence. Yet for all the sparks, the two have little chemistry, and Zellweger’s serial infidelities appear to take center stage.

The cacophony of plot lines may be explained by loyalty to the source material, a 2005 novel of the same name which Harris helped adapt into a screen play. To Harris’ credit, the movie is well paced and fun to watch. Still, as plot line after plot line recedes or meets resolution, the audience arrives at the core of the movie not by artful revelation but by process of elimination.

The true love story of Appaloosa is between Cole and Hitch. Their relationship has all the chemistry that the romance with Zellweger’s character so evidently lacks. Their easy public rapport is only half the story; behind the classic tough-guy banter hides rare tenderness and affection, revealed as Mortensen gently supplies the multisyllabic word that the less educated Harris struggles to come up with, or in Mortensen’s lingering embrace after pulling Harris out of a brawl. However, the audience only appreciates the significance of these moments at the end.

“Appaloosa” is not Harris’ first attempt at directing. In 2000 he directed and starred in “Pollock,” a biopic about the famed painter, walking away with an Oscar nomination for best actor. Marshalling the much larger set of characters and plot lines of “Appaloosa,” however, Harris struggles to emphasize Cole and Hitch’s intimacy in the noise of the movie’s serial genuflections to classic Western archetypes. His relative inexperience at directing reveals itself in other areas, perhaps nowhere more so than in Mortensen’s girlfriend: a character who serves no purpose other than to artlessly telegraph the psychology behind Zellweger’s dalliances and to prove that for all the chemistry with Harris, Mortensen isn’t gay.

For an actor to write, direct, and star in the same movie is no small feat. Achieving excellence in this creative trifecta puts one in the company of Orson Welles. The best in modern Hollywood generally do not presume to tackle more than two of the three, and even then few pursue the challenge of directing themselves in lead roles. Where Clint Eastwood and Mel Gibson succeeded, many more have struggled to overcome the immense challenge of maintaining both intimacy of character and perspective over the film as a whole. While Harris may not walk away with any statues for “Appaloosa,” he has still succeeded in creating a thoroughly agreeable moviegoing experience.