Combining the mumblecore sensibilities of their previous work with better-known actors and a decidedly mainstream through-line, writer-directors Jay and Mark Duplass (2008's "Baghead") have concocted with "Cyrus" a familiar story boasted by a smarter-than-usual script. Truth be told, the plot is nothing special—in a lot of ways, it most recently resembles 2007's "Mr. Woodcock," of all movies—and where it leads won't surprise anyone. The key to why the film nonetheless works as well as it does is in the treatment. The characters are written with grace and a respect to their intelligence, not, as so many Hollywood movies do, as flimsy constructs who must pander to insulting conventions. The raw, naturalistic handheld camerawork by Jas Shelton, full of tracking shots, zooms, and fewer cuts than the norm, brings an almost documentary-like immediacy to scenes without falling into the shaky-cam trap. Even when we feel as if we've seen it all before, there is a distinct realness about the narrative that lifts things above the mundane.

It has been seven years since his divorce to Jamie (Catherine Keener), but freelance editor John (John C. Reilly) still hasn't fully gotten over the break-up. When Jamie—still his friend—announces that she is getting remarried, it is a further blow for a lonely guy who hasn't even yet returned to the dating pool. Hoping to get him out of his funk and help him to meet new people, Jamie and fiancé Tim (Matt Walsh) drag John to a party. After a few drinks but before he performs a drunken rendition for all to see of '80s pop song "Don't You Want Me" by The Human League, John meets the pretty, vivacious Molly (Marisa Tomei). Against all odds, they hit it off—Molly previously overheard him spilling his guts to a stranger at the party and was taken by his honesty—and are soon on the precipice of regularly dating. What John does not know until he finally decides to show up unannounced at her home is that she lives with her 21-year-old son Cyrus (Jonah Hill), an aspiring musician and obvious mama's boy. Molly is nervous about how Cyrus might respond to a new man in her life, but he at first seems to take it in stride and instantly warms to John. After losing his shoes at their house and later finding them in Cyrus' closet, John realizes the truth is much different than the outward illusion. Indeed, Cyrus is seething with jealousy and is willing to passive-aggressively do whatever it takes to sabotage their romance.

A human comedy laced with bitter pills, "Cyrus" avoids slapstick, potty jokes and broad humor—you know, the sorts of things that seem to go hand-in-hand with today's studio-produced fare—and instead earns occasional laughs through keen observation and authentic, at times uncomfortable, behavior. The rest of the time, filmmakers Jay and Mark Duplass don't feel the need to even strive for such a thing, trusting that the emotions inherent within the characters' conflicts are more than enough to keep an audience watching. They're right, even when the plot does feel awfully commonplace, with John and Cyrus secretly sparring and trying to bring the other down while Molly stays oblivious to the troubles between them.

Besides that, a nice job is done in seeing both points-of-view. John, as the central protagonist, is a good, earnest man who sees his miraculous new chance at happiness threatened, and is afraid of losing Molly and being alone all over again. Meanwhile, Cyrus is a man-child who isn't yet ready to leave the safety of his mother's nest and set foot into the adult world. He's selfish and a little immature, but behind that there is a deep love and respect that he has for his mom. When the chips are down, he doesn't want to see her get hurt, even if it means doing a little sacrificing of his own. When sticky situations arise that one can see coming a mile away—Cyrus insists on attending Jamie's wedding with John and Molly, seeing it as a perfect chance to humiliate John—the Duplass' don't quite go the usual route in their payoff. And, when John comes clean to Molly about Cyrus' actions, she does not get angry, accusatory, or throw a fit, but actually listens to what he has to say and considers that maybe more is going on with her son than meets the eye. A later scene where Molly and Cyrus share a heart-to-heart and she expresses her wishes that they never lie to each other, the outcome is quietly and simply affecting. Cyrus isn't a two-dimensional monster, but someone with verifiable feelings of his own.

The quartet of main performers are terrific. John C. Reilly (2009's "Cirque du Freak: The Vampire's Assistant"), the rare actor who can seamlessly play funny and serious roles without batting an eye, gets to combine both here. Reilly is charming in a scruffy way as John; if Molly appears to be a bit out of his league, at least the film succeeds at laying out what she might see in someone like him. When Molly joins him in his initially embarrassing song performance at the party, paving the way for the rest of the guests to follow suit and start dancing, it is an exuberant moment that economically and effectively sets up their relationship and what follows. This is especially fortunate since, by the time Cyrus is wreaking havoc, the picture stops developing John and Molly as a couple and leaves them in a state of domestic stasis. As Molly, Marisa Tomei (2008's "The Wrestler") nicely underplays Molly and keeps her close, touchy-feely bond with Cyrus from getting creepy. Catherine Keener (2009's "Where the Wild Things Are") is a welcome presence no matter the role, but she is particularly winning as Jamie, retaining a caring friendship with John in spite of their divorce. Finally, for the second time in one month, Jonah Hill (2010's "Get Him to the Greek") goes above and beyond what one is likely expecting from him in relation to his past movies. If his layered, subtly poignant turn as Cyrus is any indication, Hill has what it takes to be diverse and spontaneous in his choice of roles, equipped to handle himself as a leading funnyman and a dynamic dramatic actor.

Low-key and unpushy, "Cyrus" proves to be a small cinematic pleasure, a change of pace from summer's mediocre onslaught. Overwhelming, it's not—the plot beats really are on the formulaic side, and it's neither funny nor deeply impacting enough to leave a long-lasting impression—but writer-directors Jay and Mark Duplass know what they are doing. Fiercely independent in their frame of mind, but not snobby or pretentious about it, they are able to make films that can be appreciated by art house lovers as well as commercial audiences. The ending of "Cyrus," uncompromised and forthright, cutting to black a few seconds before the norm at the precise moment when the characters' arcs are filled out and their immediate futures are suggested, is just right. Why linger and spell things out when the value of insinuation is so underrated these days?