It was the classic "Star Trek" episode "Mirror, Mirror" that first introduced the idea of an alternate reality, like the fictional world we know in many respects, but with key differences.

In that episode, it was certainly the Starship Enterprise's transporter room in which Kirk and his team materialized during that fateful ion storm — but one look at Mr. Spock in that goatee, cruelly torturing a transporter tech for his unsatisfactory performance, and it was obvious that this Enterprise wasn't our Enterprise.

That episode's "mirror universe" was in many respects pretty antithetical to "our" world, but later chapters in "Star Trek" continuity explored a wider and more subtle range of alternate realities.

The "Star Trek" universe was revealed to be a multiverse of interrelated, ever-diverging infinite possibilities — some indistinguishable from one another but for the smallest of details (the flavor of a birthday cake), others nightmarishly distant (the United Federation of Planets on the brink of destruction).

For too many years, the continuity of that one particularly well-documented universe that has hosted six "Trek" TV series and 10 feature films has been so exhaustively explored and mapped out that there was essentially nowhere else to go with it. It had become so mythology-bound that it was all but incapable of surprising us.

Which raises the head-smackingly obvious yet revolutionary question: Why stick to that universe?

And so, for the first time in forever, we have Star Trek really and truly boldly going where we haven't been before — taking Kirk, Spock, Bones, Uhura, Scotty, Sulu and Chekov on a brand-new adventure for the very first time.

Before you know it, you're getting to know old friends in an entirely new light. It's like what Alan Moore said about Frank Miller's The Dark Knight Returns: "Everything is exactly the same, except for the fact that it's all completely different."

You can call the new film, from director J.J. Abrams and writers Roberto Orci and Alex Kurtzman, a reboot, and it effectively is. At the same time, it begins with an onscreen, plot-level mechanism diverting this continuity from the one we know all too well.

It's a bold, startling opening, an introduction to James Tiberius Kirk I wasn't expecting, and it opens the movie with a wallop both narratively and emotionally.

The energy of the opening carries right into the next scene and the one after that, blending action, character development and humor with remarkable deftness. In fact, the film's mercurial vitality seems almost to flow from its youthful protagonist, the young James T. Kirk, brilliantly played by Chris Pine.

Kirk's jaunty forwardness and impulsive audacity are accentuated here by growing up fatherless in Iowa farm country. The Kirk played by Shatner, who knew his father, evidently absorbed similar traits from the old man, but perhaps channeled them more responsibly and maturely. This Kirk, reckless and immature, has a way to go, though old Captain Pike (an authoritative Bruce Greenwood) can see that the boy is his father's son and has what it takes — if he cares to extend himself.

Whether Spock (uncanny Zachary Quinto) has also somehow had a different upbringing in this timeline is impossible to say, but Abrams and company explore sides of his identity crisis growing up that I haven't seen before, including Vulcan bullying.

Spock's conflicted meta-emotions, his desire to distance himself from his human side without distancing himself from his human mother, and his delightfully ironic embrace of a most Vulcan gesture as a way of expressing solidarity with his mother offer a persuasive and satisfying take on a character that may be the franchise's most compelling — one that holds up admirably even when the one and only Leonard Nimoy shows up as "Spock Prime," the old Spock of the familiar universe.

It's entirely logical that when the young Kirk and young Spock of this continuity meet at Starfleet Academy they should have nothing but contempt for one another — particularly when Kirk pulls his famous Kobayashi Maru stunt, beating the unbeatable test as described in Star Trek II: The Wrath of Khan. (The Kobayashi Maru scene itself is one of the movie's few miscalculations, though, since Kirk's jokey frat-boy insouciance in that scene makes it a juvenile prank rather than a subversively idealistic denial of "no-win scenarios.")

Kirk's well-known womanizing gets some comeuppance as he repeatedly hits on Uhura (assured Zoe Saldana), who refuses to give him her full name, and there's a brief, abortive bedroom scene that — a bit like a similar scene in Iron Man — is more about showing up the hero's foibles and shortcomings than celebrating his way with women (á la James Bond).

As the story swings into action, we meet an already irascible Dr. Leonard "Bones" McCoy (Karl Urban, shedding Éomer to channel DeForest Kelley), Sulu (John Cho), Chekov (Anton Yelchin) and finally Scotty (hilarious Simon Pegg).

Humor runs high among the supporting cast, though Kirk gets his share of the fun, notably in a sequence of jaw-dropping physical humor as Bones tries to finagle a seat on the Enterprise for the grounded cadet Kirk, and in a moment of unexpected absurdity when Scotty's first minutes on the Enterprise almost become his last.

There's also plenty of action, from starship dogfights to an exhilarating space dive with retractable parachutes and perilous hand-to-hand combat on a narrow ledge of a space drill high in the stratosphere above Vulcan.

Eric Bana plays a rather generic alien menace, a tattooed Romulan named Nero, and, at some point, the story begins to falter as coincidences pile up and certain points don't quite jibe.

By the time Kirk meets old Spock on an ice planet, it's clear that, as reboots go, Star Trek isn't in the same league as, say, Batman Begins. As brilliantly as Abrams and company have reimagined the world of "Star Trek," they haven't crafted a story within that world with the thematic resonance of The Wrath of Khan, The Search for Spock or even The Voyage Home.

And yet compared to any but the most brilliant origin stories — compared to the modest pleasures of Iron Man, say — Star Trek delivers superbly, while opening the door to the possibility of better things yet to come. Where a typical franchise prequel like Wolverine merely hits the expected numbers, Star Trek surprises and delights. That's something "Star Trek" hasn't done in a couple of decades or so. I'll take it.

Steven D. Greydanus is editor

and chief critic at DecentFilms.com.

Content advisory: Much action and sci-fi violence; a brief, abortive bedroom scene (nothing explicit); ogling a lingerie-clad woman; a few coarse references. Could be okay for mature teens.