Every once in while, a movie comes along that speaks to the great and universal fear lurking at the 1,000-crunches-a-day core of youth-obsessed Hollywood.

Those anxieties are remarkably close to the surface in Gemini Man, which finds superstar Will Smith squeezing the prince to see if he’s still fresh. He stars as Henry, an aging hit man who — feeling 50 and beset by graying temples and diminishing powers — suddenly finds himself stalked and pursued by a younger, fitter version of himself.

The younger man is also played by Will Smith (de-aged by computers), and though the plot is nominally about assassins and Jason Bourne-like intrigue, the high-tech spectacle offers parallel insights into the vulnerabilities of mature stars — Gemini Man is not just Henry versus a facsimile, it’s Will Smith versus the unlined face of his youthful self.

The doppelganger, known only as Junior, chases Henry through the streets of Cartagena in the movie’s big action-sequence opener. Henry is somewhat alarmed by an adversary whose skills are identical to his own, but he’s highly alarmed by the uncanny resemblance and the age difference.

“Did they show you a picture of me?” he asks Junior, between bullets.

“Yeah,” taunts Junior. “You look old.”

Ouch. That hurts worse than the near-death butt-whooping that old Henry suffers at the hand of look-alike Junior, until Henry’s allies (Mary Elizabeth Winstead, Benedict Wong) intervene to save his life. There are more confrontations to come as the goofball plot takes the cast to Hungary (where mysteriously all meetings must be conducted in bathrobes) and back to the States, where a madman (Clive Owen) is building a mercenary army using bio-ethically dubious technology.

The last time we saw something this attuned to the delicate psyche of a major Hollywood star was Oblivion, headlined by Tom Cruise, who in the movie is stricken by a nightmarish glimpse of a world full of a million other Tom Cruises. You can divvy that up any way you want — 500,000 Jerry Maguires, 500,000 Mavericks — the point is, it’s a chilling scenario for an actor who’s spent his career advancing the idea of the one and only Tom.

» READ MORE: 'Oblivion': Handsome Cruise to nowhere

Oblivion, though, was primarily concerned with imitation. Gemini Man is more focused on age, youth, displacement. Junior, for Henry, is the looming avatar of the inevitable.

“He’s like the mirror you don’t want to look into," says Winstead’s character, invoking vanity in a way that clearly speaks more to the priorities of the movie industry than the assassin’s trade. In that vein, Henry’s concerns about a former boss could easily echo Smith’s concerns about a fickle producer.

"He knew one day I’d get old and he’d need somebody like me,” Henry frets.

The good news for Smith is that the technology deployed in Gemini Man — one that could theoretically allow all actors to be duplicated and replaced — is not yet seamless. Junior has the voice and cockiness of the Fresh Prince, but he has the strobe-y imperfections of a slick video-game imitation.

It should be noted that I saw this movie in a standard format — there is a fancier 3D IMAX version shot by director Ang Lee in a super-fast 120 frames per second, and perhaps at that speed Junior is more convincing.

Perhaps it’s just as well. Digital innovations make actors younger, but I remain stubbornly older, with ancient eyes and faulty synapses, and 120 frames per second are more likely to produce a headache than amazement.

Also, if I want to know what Will Smith looked like in his 20s, I can always return, happily, to Men in Black.

Gemini Man. Directed by Ang Lee. With Will Smith, Mary Elizabeth Winstead, Clive Owen and Benedict Wong. Distributed by Paramount Pictures.

Running time: 1 hour, 57 mins.

Parents guide: PG-13 (violence)

Playing at: Area theaters.