The public’s fascination with William Bonney, aka Billy the Kid, seems boundless, at least if one judges from the number of movies made about his short, violent life. The latest is this western directed by actor Vincent D’Onofrio, who also takes a supporting role in the picture as Sheriff Romero of Las Vegas, one of the lawmen trying to collect on the Kid’s bounty.

The cheeky contrivance of Andrew Lanham’s script is that the kid of the title isn’t Billy at all, but a fictional youngster named Rio Cutler (Jake Schur), who, along with his sister Sara (Leila George) falls in with Billy (Dane DeHaan) and his cutthroat gang just as they are about to be captured by Sheriff Pat Garrett (Ethan Hawke) and his posse late in 1880. Rio’s story is folded into the period from December to July, 1881, when Billy escaped jail, only to be tracked down again and fatally shot by Garrett under suspicious circumstances.

Rio’s narrative actually opens the movie; he kills his father as he’s drunkenly attacking his mother, and then runs off with Sara to avoid the wrath of their psychotic uncle Grant (Chris Pratt), the owner of a saloon and brothel. During their escape they take refuge in the cabin where Billy and his gang soon hole up, and become part of Garrett’s party when Billy is forced to surrender. As such he not only watches as the final act of the drama plays out, but becomes involved with both men—and must decide which of them he should trust and take as his role model when his sister is captured by Grant and dragged back to a fate worse than death.

“The Kid” thus becomes a morality play as well as a coming-of-age story, all wrapped up in the conceit of happening within the historical context of the Bonney-Garrett showdown (a context that, at least, the screenplay manages to stick fairly close to). That’s an ambitious load for the movie to carry, and it isn’t entirely successful in managing the task. It strives for the depth of “Unforgiven,” but falls considerably short of that standard. (And while its message that one should take responsibility for one’s actions is certainly unexceptionable, its final suggestion about how one should act in difficult circumstances is at best problematic.)

Much of the reason for that is D’Onofrio’s direction, which tends to be sluggish, emphasizing the pretentiousness of much of the writing (Pratt, for instance, has a mini-monologue toward the close—about bluebirds, no less—that’s almost laughable—and it’s not alone in that respect). And D’Onofrio allows—probably encourages—long pauses in the delivery of dialogue that accentuate the problem, forcing the cast to affect a profundity the material never actually earns.

That hobbles Hawke, who seems so determined to appear haggardly iconic that the result is more effortful than persuasive. DeHaan makes Bonney a rough-and-ready character and is unafraid to look a mess, but there’s a lack of discipline to his turn that saps it of credibility; the most convincing part of the performance is the odd hat he wears, familiar from the sole photograph of Billy that’s survived, but it looks ill-fitting on DeHaan, making for more of a costume-party impersonation. Pratt snarls as the evil uncle, but comes across a mite ridiculous given the massive beard through which he must deliver that goofy soliloquy at the end.

Unfortunately, at the center of things young Schur is seriously overparted. The boy tries hard, but his most intense moments feel awkward and amateurish. The supporting cast is okay if unexceptional; Adam Baldwin shows up among them as one of the lawmen who meet an untimely end at Billy’s hand.

“The Kid” has an appropriately grubby look, courtesy of production designer Sara K. White, costumer Ruby Katilius and especially cinematographer Matthew J. Lloyd, whose widescreen images make good use of the locations’ dust and grime. It also has going on twenty producers listed in the credits, almost equaling the number of years William Bonney actually lived.

In the end, however, D’Onofrio’s film tries to do too much, and ends up overloaded and plodding. It’s an example of a clever premise foiled by self-indulgent execution.