One of the biggest surprises of this year’s Sundance is just how terrific Safety Not Guaranteed, Colin Trevorrow’s film based on a real Craigslist ad seeking a companion for time travel, turned out to be. The film’s quirky premise, which sends three magazine employees to investigate whether the man who placed the ad really thinks he can travel through time, seems funny enough just based on the premise (and it is), but like the writers who go off in search of what they think will be a wacky story to poke fun at, we find instead a very human film that’s complicated and genuine and never cruel in its use of humor. I thought this was by far the strongest script at this year’s Sundance in terms of sheer quality of writing and execution of idea, and apparently I wasn’t the only one; screenwriter Derek Connolly won the Waldo Salt Screenwriting Award for Safety Not Guaranteed at last night’s awards ceremony.

Parks and Recreation‘s Aubrey Plaza carries much of the film as Darius, a cynical intern roped into traveling to the shore town of Ocean View, Washington with fellow sad sack intern Arnau (Karan Soni) and their annoyingly smug and smarmy boss Jeff (Jake Johnson), who really pitched the story so he’d have a paid trip to Ocean View to hunt down ex-girlfriend Liz (Jeneca Bergere), the first teenage romance that he’s never quite gotten over.

The three writers stalk and hunt down their target, Kenneth (Mark Duplass) and Darius is pegged to make contact with him. And she does, in a hilarious, brilliantly written comedic scene in which she approaches Kenneth as he’s stocking soup at his day job at Grocery Outlet, and convinces him that she is the one to go on his time travel mission with him. But the more she gets to know Kenneth, the more she likes him. She’s no longer so cynically certain Kenneth’s a nut case, and what’s more, his paranoid delusions about government agents following him might not be so paranoid after all. As Darius’s feelings about Kenneth and the story she’s investigating grow more complicated, so too do Jeff’s for Liz. At first Jeff is disappointed to see that Liz – like him – has actually changed and aged a little over the past twenty years, but as he gets to know the woman who’s grown from the girl in his memory, shallow Jeff starts to see Liz in another way.

Side stories like this can detract from the storyline of the protagonist, but here Jeff’s budding new relationship with his old love is used to enhance the underlying theme of not judging others by first appearances, and learning that even someone who might seem to be flawed in some way might still have something special to offer. The Jeff sideline is a smart choice from a writing standpoint also, in that it allows this character who would otherwise be merely an annoying one-dimensional prop to have a richness and complexity that’s often neglected in secondary characters.

What I most enjoyed about Safety Not Guaranteed, though, is a performance by Mark Duplass that made me see him as an actor in a completely different way. He’s always likable, generally funny, and undeniably talented, and yet in most of his roles there’s still that little bit of “Mark Duplass” under the surface peeking out. His turn in Safety Not Guaranteed, though, is a bit of a revelation, much more complex and layered than we’ve seen from him before. In his hands, Kenneth is quirky and funny, which you’d expect from Duplass, but he’s also deeply flawed, sad, and utterly sincere. Between this role and his role as a guy mourning his dead brother in Lynn Shelton’s Your Sister’s Sister, this is the year for me that Mark Duplass has become more than just another indie hyphenate; he’s stepping up into “seriously good actor” territory.

This is just a solid film all the way around: the strong confident direction by Trevorrow, the terrific script by Connolly, gorgeous cinematography by Ben Kasulke and some really excellent production design by Ben Blankenship and art direction by Lisa Hammond (the design work on Kenneth’s house is particularly noteworthy). Safety Not Guaranteed is a cut way, way above the average Sundance film. When it makes its way to your neck of the woods, I’m betting you’ll enjoy it a lot. Pretty much guaranteed.