From a distance, all signs indicate that “Alpha Dog” should be an atrocious movie. Its fall release was pushed back to early January, the cinematic equivalent of being dumped for Scarlett Johansson. The plot is based on a publicized true story, so most in the audience are aware of the ending. Despite being a gritty, teen murder drama, the cast list looks like the bastard offspring of the Disney Channel and MTV. Perhaps most damning, it stars Justin Timberlake. Nevertheless, the story somehow succeeds in being both captivating and satisfying (at least until the last half hour), the acting manages to be impressive and the film ultimately entertaining.

Anyone who has seen a trailer or commercial for “Alpha Dog” or has read a newspaper article about the controversy surrounding the pending trial knows the movie is based on the true story of the kidnap and eventual murder of Zack Mazursky (Anton Yelchin).

Because his older brother has run up a debt of a few thousand dollars, Zack is kidnapped by a gang of rich, attractive, “bad-ass” white kids led by Johnny Truelove (Emile Hirsch). As it so happens, however, Zack is fed up with his overprotective mother (Sharon Stone) and stays kidnapped willingly to party with his new friends, even when offered the chance to go home. In his follow-up to “The Notebook,” director Nick Cassavetes shows he is capable of an entirely different genre: Even though viewers know from the beginning that Nick will not make it through the movie alive, Cassavetes still draws the audience’s interest into the character.

After the gang impetuously decides to kidnap Zack, it is alternatingly funny and painful to watch them illogically try to figure out what to do next — every aspect of the crime is essentially post-meditated. Each witness the gang runs into (the tally reaches 38) is identified and tagged, accentuating exactly how poorly thought out the plan was. Cassavetes — doing double duty as a screenwriter — seems to voice this concern as Johnny complains to his sidekick Freddy (Justin Timberlake — insert “SexyBack” pun here), “There’s a solution here, maybe I’m just not seeing it,” an acknowledgement of the frustration the audience feels.

By emphasizing the recklessness and stupidity of the act, though, Cassavetes switches the focus of the movie from a crime already known to the audience to an exploration of how the lives of privileged kids can get so off-track. Cassavetes opens the film with a montage of toddlers happily playing, contrasting, albeit heavy-handedly, the innocence of youth with serious misbehavior in young adulthood. “Alpha Dog” places blame on parents — as Johnny’s father (Bruce Willis) and his grandfather (Harry Dean Stanton, from “Big Love”) provide him with drugs to sell to fund his operation — and the media (although “the only thing they’re shooting is music videos”) as well as ultimately illustrating how dangerous teenage social circles can be if left unmonitored.

What is most impressive about “Alpha Dog,” though, is that it is persuasive without seeming to preach. It manages to feel authentic, despite its bevy of pampered young actors recognizable mostly to fans of the Teen Choice Awards — that is, until the end.

The closing scenes are tedious because they exploit audience’s knowledge of the inevitable ending to an unnecessary and unsubtle degree. Bad acting, most notably that of Sharon Stone clad in a fat suit and Marissa Cooper’s former lesbian lover Olivia Wilde, drag down the something even further. The film, however, does feature Timberlake’s surprisingly three-dimensional theatrical debut, and Anton Yelchin’s performance is worth the price of admission.

Ultimately, the film’s first hour is interesting enough to save “Alpha Dog” from the drudgery of its final scenes. The entertainment value, though, is of little consolation to the family of the victim: Zack’s mother has tried to commit suicide three times since the film’s release, and his father claims the movie “glamorizes [his] son’s death and allows celebrities to cash in on a brutal, evil murder” — certainly a somber aftermath to an otherwise thoughtful, provocative film.