If one's high school graduation isn't signifier enough of childhood's end, a person's ten-year reunion is a decidedly defiant symbol of adulthood. A rite of passage that makes no difference if you actually attend or not, said anniversary stands as a sobering reminder of how quickly time has passed. Are you where your 17- or 18-year-old self thought you'd be? In what ways have you changed? And what do you hope to still accomplish? For the characters in "10 Years," their hometown commencement starts with fun and games and lots of drinking as some of them see each other for the first time in a decade, but as the night wears on, there is a nostalgic sadness that creeps in. In this moment, they're with their old friends, but their celebration is mostly just a fleeting facade. Very likely, they won't ever be in the same room together again. "10 Years" is inordinately wise about this specific feeling, at this particular moment in time. There have been many movies about class reunions—1997's "Romy and Michele's High School Reunion" is a comedy classic, while 2012's "American Reunion" covered some of the same territory just recently—but none have felt quite so candid and close to reality as this one.

Lake Howell High School's Class of 2002 is getting back together, and for most that also means a long-awaited homecoming. Mortgage broker Jake (Channing Tatum) has a cushy job and a lovely girlfriend, Jess (Jenna Dewan-Tatum), who has agreed to accompany him, but secretly he's holding out hope that his old high school flame, Mary (Rosario Dawson), might show up. Does he think they will get back together? Not really, but it would be nice to see her again, if only to clear up why he so rashly pulled away from her after graduation. Before the reunion proper gets underway, Jake hooks up with his friends at the home of Cully (Chris Pratt) and Sam (Ari Graynor), now married and with two children. Cully was a bully back in the day and has made it his mission to apologize to everyone he used to make fun of. Sam, quite accurately, thinks the idea might blow up in his face and urges him not to come on too strong. Also there: New York stockbroker/bachelor Marty (Justin Long) and betrothed best bud AJ (Max Minghella), going swag for the night; Scott (Scott Porter), back from his new home in Tokyo with girlfriend Suki (Eiko Nijo) in tow, and successful singer-songwriter Reeves (Oscar Isaac), now something of a town celebrity. Once at the reunion, several more classmates come into focus: Julie (Kelly Noonan), who is hosting the reunion and hanging by a thread; Garrity (Brian Geraghty), whose new wife Olivia (Aubrey Plaza) is taken aback to learn several juicy tidbits about his teenaged days she never knew before; party girl Anna (Lynn Collins), whom Marty and AJ latch onto; and Elise (Kate Mara), an outsider in high school who isn't quite sure why she's decided to come back when few people even remember her. Oh, and much to Jake's anxious anticipation, Mary does show up, but she's not alone: she's brought her slightly older husband, Paul (Ron Livingston).

The directing debut of Jamie Linden (screenwriter of 2010's "Dear John"), "10 Years" is an ensemble slice-of-life in every sense of the phrase, a free-floating tour of a somewhat strange but universal experience. Playing out as if Robert Altman's interconnected style fused with John Hughes' wistful sensibilities on growing up, the film begins with little fanfare and the introduction to a cast of characters who initially strike as either a little too cardboard or a little too obnoxious. The rest of the movie, however, works to strip these initial preconceived notions from the faces of people who are altogether more complicated, multidimensional and sympathetic than expected. If the opening couple acts are little more than like eavesdropping on a real-life small-town reunion, writer-director Jamie Linden gets the rhythms, the trepidation, and the conflicting sense of being out of place and right where you are supposed to be exactly right. All of the little reunion details are accurately on display, too, from the picture-taking corner in front of a giant "10" emblem in the foyer to the photos littered about from their high school class. As the characters make their way around the indoor venue, making small talk and trying to fit in, it is as if they're transported right back to high school. They might have emotionally matured for the most part—though the drunken Cully makes a good case for someone who hasn't—but when it comes to just wanting to fit in, the pressures that come along with being around our peers never totally changes.

Eventually, the reunion settles down and the gang decides to continue the party at a karaoke bar called Pretzels. It is here, just as the third act begins to rear its head, where "10 Years" both settles and deepens into a motion picture much more searing and poignant that one might have guessed, the earlier sections a deliberate but necessary precursor to the dramatic wallops yet to come. No, there are no matters of literal life and death, and the question of whether Jake and Mary are going to reignite their flame is kept a wise non-issue. There are surprises, though, some of them uncanny, others appropriately heart-tugging. For Reeves and Elise, who have been flirting all night (they once shared a class together), Reeves finds it refreshing that Elise isn't familiar with his music because he knows she has no ulterior motives, while Elise is happy to learn that she at least left an impression on someone back in high school. What she doesn't yet understand is the full scope of the imprint she made—a revelation that comes to a sublime head when Reeves agrees to go onstage and sing his hit song "Never Had." It's an unforgettable moment. Meanwhile, Sam's love for Cully and her need to be the grown-up and take care of him makes for a fascinating dynamic. She is reminded throughout the night of the uncouth, at times insensitive, person Cully can be, but also of his earnest heart underneath. Indeed, his hopes of making amends are ultimately upended by his unchangeable personality: he's naturally something of an ass. And then there's Scott, who announces that he'll be returning to Tokyo—the home he loves now—and that his parents are thinking of joining him there. With no one left to come back for, this might be his last time in the town he grew up in. For Scott, it's a time of excitement, of looking ahead. For several of his classmates, the news is more sobering. With their adolescent connections severing, it is the end of an era for all of them.

In a film that spreads the wealth fairly evenly to all of its central actors, Channing Tatum (2012's "Magic Mike"), who also earns a producer's credit, is the individual the narrative begins and ends with, the opening and subsequent closing of his car's glove compartment a fitting bookend that brings around full circle Jake's lingering hang-ups and the control over his future he finally takes. As girlfriend Jess, Jenna Dewan-Tatum (2006's "Step Up") sweetly plays a young woman who gamely wants to support her beau, but also knows when it's time to step back and let him have time with those that he hasn't seen in years. In a lesser, dumber script, Jess would have been written as snooty or domineering; instead, there is never a doubt that she is good enough for Jake, and vice versa. They belong together. As Jake's ex, the now-taken Mary, Rosario Dawson (2011's "Zookeeper") blesses her character with an underlying pathos that comes to the forefront at Pretzels, when the delicate events of their bittersweet prom night are revealed. Ari Graynor (2012's "For a Good Time, Call...") plays against-type as Sam, the actress' usual brassy personality softened to portray a young mother who sometimes can't help but feel like her husband is her third child. As said hubby Cully, Chris Pratt (2012's "The Five-Year Engagement") has never been better, bringing sadness and embarrassment to a man who knows he wasn't very nice in high school and wants to make it up to those he terrorized. What the hard-drinking, well-meaning Cully doesn't stop to realize is that he's still pretty much the same frequently insensitive guy he always has been.

Fine performances don't stop there: a layered, affecting Lynn Collins (2012's "John Carter") plays Anna, sweeping into the reunion looking to impress while shielding the things in her life that have forced her to grow up too quickly; Aubrey Plaza (2012's "Damsels in Distress") brings her deliciously dry sense of humor to Olivia, learning more than she could have ever guessed about her husband Garrity, and, best of all, Oscar Isaac (2011's "Drive") and Kate Mara (2010's "127 Hours") spark like fireworks as Reeves and Elise. Though Isaac has come back to town a newfound star, he feels like the outsider that Elise always has been, unsure if anyone would care about him if he weren't in the public eye. Elise, meanwhile, never cared for school and can't quite believe she's attending the reunion at all; looking at the sole picture of herself hanging on the photo wall (she's in the background, wearing her signature yellow high heels), Elise marvels how even there, she looks like she can't wait to get out. The chemistry between Isaac and Mara, the latter emanating a warmth and soulfulness you just want to hug, carries through the proceedings until a payoff near the end that should have the most hardened of viewers swooning.

"10 Years" is set over an approximate 12-hour span, but within that limited time are incalculable truths and epiphanies that may aid in informing the entire next chapter of the characters' lives. As things wind down over Passion Pit's rhapsodic, pared-down cover of The Smashing Pumpkins' "Tonight, Tonight," the collective group has become much more than various sketches on a page, resembling people that all of us have either known or met (or maybe, just maybe, one of them is ourselves looking back). A full-blown entertainment of observational humor and relatable poignancy, the film works as well as it does because of how keenly rooted it is in the unpredictability of reality itself. In the end, "10 Years" has grown to resemble a kaleidoscopic collection of memories, none of them worth forgetting.