Star quality can't be taught. Some people just have it, and it's obvious from the first time you see them. It's Tom Cruise sliding down the hallway wearing shades and skivvies in Risky Business. It's Marlon Brando overpowering Vivien Leigh both physically and emotionally in A Streetcar Named Desire. It's Brad Pitt making Susan Sarandon, Geena Davis, and your mother weak in the knees during his few brief scenes in Thelma & Louise. And, for your comic book heads, it's Chris Hemsworth coming out of nowhere to turn Thor, the least likely of Marvel movie anchors, into the one Avenger every dude wants to look like and every woman wants to look at.

Last night, the few hundred people inside Austin's Stateside Theatre caught a similarly transcendent, star-is-born performance. The film was The Guest, the latest indie collaboration between You're Next director Adam Wingard and screenwriter Simon Barrett. The man you want to look out for is Dan Stevens.

A midnight-dark comedy that straddles the line between being a psychological thriller and an bombastic, '80s-minded action flick, The Guest revolves around a character named David (Stevens), an Army soldier who's recently been discharged from service in Iraq. Back in America, he heads straight to the home of a fallen military friend, Caleb to let them know their son/sibling loved them, and to help them in any way he can. David, as it turns out, is also something of a one-man wrecking crew, able to beat the piss out of a room full of guys one minute and handle guns like a possessed Charlton Heston. He ingratiates himself into the family's world, helping Caleb's antisocial younger brother deal with high school bullies, partying with the 20-year-old sister's drug-using friends, and drinking beers with Caleb's professionally frustrated father. But then the blood starts flowing and buildings begin exploding, and Caleb's family learns firsthand that David's not what he seems. Their knight-in-shining-armor, the find out, has more in common with The Terminator.

Dan Stevens, the force behind David, is an English actor best known for his role as the prim Matthew Crawley on that English small-screen phenomenon Downton Abbey. Fans of that period drama will most likely feel a certain way after seeing the name Matthew Crawley, since the beloved character famously died last year on the show, much to viewers' shock and despair. Stevens didn't waste any time switching over to films, quickly landing the lead in The Guest.

Downton Abbey's loss, film lovers, is your gain.

From the moment he rings Caleb's family's doorbell minutes into The Guest, Stevens exudes that kind of star power very few actors have, and even fewer are ever able to put on screen. Uppity, proper Matthew Crawley is no more—in his place stands the ultimate badass.

Much credit goes to writer Simon Barrett, of course, for penning a character as fascinating, complicated, and unpredictable as David. Just as easily as David can charm the family's matriarch (Sheila Kelley) with an onslaught of "yes, ma'am" pleasantries, he can stare into a douchebag guy's eyes with penetrating menace, and Stevens sells both sides of the character's tricky demeanor with seemingly effortless command. He looks like Ryan Gosling, captivates like a young Tom Cruise, and whoops ass like Jason Statham.

The Guest is, as a whole, a finely calibrated work of mashed-up genre entertainment, just as good, if not slightly better, than Wingard's previous crowning achievement, the lively and intelligent home invasion subversion You're Next. There's no denying that about the film. Yet, watching Dan Stevens completely own every second of Wingard's movie, it's hard not to think that Stevens seems transplanted into the production from some A-lister factory, dominating scenes he shares with a strong ensemble of character actors (Lance Reddick, Leland Orser) and undeniably talented newbies (Maika Monroe, Brendan Meyer).

Wingard's clearly aware of his leading man's domineering presence. The Guest's soundtrack, an assortment of original synth-heavy '80s nostalgia and preexisting synth-heavy '80s songs, fuels the film with an ever-present cool-guy pulse, from which Stevens benefits the most. There are numerous shots of Stevens walking into rooms backed by jams that would be at home in Miami Vice: The Emo Version, variations of songs like Desire's "Under Your Spell" (heard in Drive). Wingard's best moment of score complementing Stevens' starriness has David rolling a couple of grenades into a diner as if he's bowling for pins and accompanied, bizarrely and rather brilliantly, by Stevie B's "Because I Love You." 

Last Friday, right when SXSW opened up, it was announced that The Guest was picked up for distribution by Picturehouse, meaning you'll definitely get a chance to see it sometime this year. Consider this your warning—if you've never watched Downtown Abbey you'll be a Dan Stevens fan by the end of 2014, and, if you're partial to smart genre hybrids, The Guestwill be under serious consideration for your inevitable "favorite movies of the year" list.

This year's SXSW Film Festival is brimming with damn good movies, but it'll be difficult to find one as fun and enjoyable as The Guest. Mainly because it's the only film screening in Austin that stars Dan Stevens.

Written by Matt Barone (@MBarone)

For more of Complex Pop Culture's SXSW coverage, click here.