A “Twilight Zone”-ish tale about fate told in the twee New Agey style of the modified mumblecore movement, the Duplass brothers’ “Jeff, Who Lives at Home” mixes geniality and poignancy to mixed effect. Its low-key, careless tone is mildly amusing, but ultimately the movie comes across like a meandering fantasy that doesn’t really earn its would-be revelatory punch-line.

Jason Segel, looking flabbier and more ungainly than usual, plays the title character, a thirty-year old dreamer who still lives in his mother’s basement and spends his time reflecting on how all things are interconnected, using M. Night Shyamalan’s “Signs” as a sort of explanatory (if enigmatic) text on the subject. A demand from his hard-working mother Sharon (Susan Sarandon) that he get off his behind, take the bus to Home Depot and buy some wood glue to fix a broken shutter combines with a wrong-number phone call for an unidentified “Kevin” sends him on a goofy adventure to find an answer to what it all means.

His peregrinations lead him to a chance meeting with his apparently better-adjusted brother Pat (Ed Helms), who’s having trouble with his wife Linda (Judy Greer) over his reckless purchase of a Porsche. When the two spy Linda having an apparent tryst with another man, Pat insists that they follow the couple to find out what’s going on, with disastrous results. Meanwhile Sharon finds herself the subject of attention at work from a “secret admirer,” which brightens her attitude in unexpected ways. The plot threads all come together in a finale that leaves Jeff satisfied that he’s learned his place in the universe—and everyone else oddly improved by the experience as well.

The picture is anchored by Segel’s cannily phlegmatic performance, which actually manages to make slacker lethargy an adorable quality, though he’s certainly helped by Helms’ hyper-energy, which serves as a nice comedic balance. Sarandon is luminous as a middle-aged woman looking for some improvement in her lot, and while the shifts in her character would bother any actress, Greer copes with them as well as can be expected. The simple, sometimes positively shabby production (shot in Baton Rouge without any attempt at glossiness by Jas Shelton) adds to the shambling charm of it all, though Michael Andrews’ score, with its excess of tinkling xylophones, lays on the whimsy entirely too much.

“Jeff, Who Lives at Home” is a significant notch more conventional than the Duplass’ earlier pictures, but it’s still going to seem strangely ragged and rambling to audiences accustomed to Hollywood’s far more aggressively in-your-face comedies. It’s a respite from them, but even at a mere eighty minutes can also be a respite that goes on awfully long.