Jeff -- who lives at home -- is the mumblecore version of a hero, or maybe rather a kind of martyr: a downtrodden slacker whose arrested development is as much a product of his goodhearted self-sacrificing as it is a steady diet of bong hits and infomercials.  

"Do you ever get a feeling that you've waited your whole life to find your destiny, but when you finally do, it's not that exciting?," Jeff (Jason Segel) asks at one point, just before something that qualifies as pretty darned exciting does happen.

"Jeff, Who Lives at Home," the fourth and (ironically) most grown-up feature from brothers Mark and Jay Duplass, reads as something of a parable -- but only in retrospect. The story unfolds over a single day, the narrative propelled by Jeff's mundane chore of fetching wood glue for his mother (Susan Sarandon), a widowed office drone who spends most of the film tethered to a drab cubicle.

Along the way, Jeff is joined by his older, Porsche-driving brother Pat (Ed Helms) after a chance encounter outside a Hooters restaurant.  Facing obstacles that are by turns both slapstick and tragic, the brothers abandon the wood glue errand for a gonzo spy mission involving Pat's wife and a man who may or may not be her lover. Throughout the misadventure, Jeff is preoccupied by what he believes are traffic signals from the universe, which Pat, sometimes viciously, dismisses as pot-fueled delusions.

Jeff has tasked himself with no less than discovering the meaning of life -- his own, at least. Driven by an obsession with the unintentionally comedic M. Night Shyamalan film "Signs," the overgrown man-child claws for meaning everywhere he looks; desperate for deeper connections but self-isolating in his single minded quest. 

It was only a matter of time before the eminently bankable Judd Apatow regular branched out into more serious roles: as Segel said himself in a Daily News interview, "Jeff is really on the dramatic side of the drama-comedy line."

You might also say that "Jeff, Who Lives at Home" begins as a comedy and ends as a drama. Indeed, the stakes get higher and higher as the film builds towards a breathless climax; by then you might find yourself with a sense of claustrophobic anxiety similar to that of characters on the screen.

All of the actors are equally wonderful, as if they made a pact before filming not to outshine each other. Sarandon's Sharon is refreshingly -- perhaps implausibly -- free of bitterness for someone whose life hasn't gone as she'd hoped; her strange and lovely subplot adds some needed texture to the story and allows Sarandon to break new ground as an actress.

Judy Greer -- who has done the near-impossible by successfully outgrowing the sidekick role to become a leading lady in her own right -- is sympathetic and relatable as Pat's frustrated, put-upon wife. Helms channels some of the simmering rage beneath the fragile surface of his character in "The Office," but here it's pinned to a vulnerability and baseline decency that keeps you rooting for him even when he's at his most awful.

Coming on the heels of "The Muppets," Segel is at a sweet spot in his career where he can do no wrong; and he certainly doesn't here. While you may scoff at Jeff's bumbling metaphysical meanderings, Segel's undeniable warmth helps a game-changing conclusion recast his character as something close to a mystic of the everyman.  Yes, Jeff lives at home, but don't we all?