It's an unwritten rule that we're supposed to feel most in step with people our own age, as if sharing the same cultural and historical references somehow enables our ability to look into one another's hearts. So why do we sometimes tumble into deeper friendships with people who are 10 or 20 (or more) years our junior or senior? Lynn Shelton's Laggies, based on a script by Andrea Seigel, sidles up to that question without ever asking it overtly. It doesn't really need to: Instead, it simply shows us moments of connection between unlikely people, laying out several kinds of loneliness in all their stripes.

The loneliest character of all — though she doesn't realize it at the beginning — is Keira Knightley's Megan, a late–20-something who has just earned an advanced degree but still has no idea what she wants to do with her life. She lives in her hometown, Seattle, doing truly menial work for her accountant father (Jeff Garlin) — she's a sign twirler, and she turns this tedious task into a blasé dance routine. Megan's longtime boyfriend, Anthony (Mark Webber), wants to get married, and although she loves him, there's something in her that rails against the life he's offering.

Part of the problem is that her old friends — a gang to which Anthony also belongs — are so busy planning ridiculous weddings and sprouting baby bumps that they can hardly believe that she, too, doesn't want these things. They've also collectively lost their sense of humor, taking offense when Megan does silly stuff, such as tweaking the nipples of a naked Buddha in a Chinese restaurant. “Buddha is sacred to a lot of people!” hisses the most uptight of them, a prissy bride-to-be played by Ellie Kemper.

Recognizing that she may no longer have a place in her old pack, Megan falls in with a bunch of high schoolers, among them Chloë Grace Moretz's orphan-eyed Annika. Megan distracts herself with their problems — their love troubles, their anxiety over parental discord — while she takes a breather from her own issues, though she's not prepared for one giant, complicating factor: She finds herself attracted to Annika's dad, Craig (Sam Rockwell), an abrasive, high-strung lawyer who's still smarting over his own marital disillusionment.

Shelton is particularly skillful at telling stories about people lost in their personal present, such as the perplexed, anxious characters in Your Sister's Sister (2011): Should I have a baby? Should I try to turn a close friendship into romance? Should I sleep with an attractive woman when the opportunity arises?

The problems in Laggies are different but hardly less bewildering. If Megan, a certified grown-up, can't find her place in the world, what hope does Annika have, particularly when she, like her dad, is still stewing over her mother's abrupt and cruel departure?

But even though Laggies is clearly well-intentioned — and the anxieties it tussles with are completely believable — the film is awkward in ways that are sometimes charming and sometimes off-putting. For the most part, Moretz and Knightley have a cozy, sisterly rapport; they're partners in crime, united against the idiocy of the world. But neither performance fully blooms on its own. In some scenes, Moretz's Annika seems knowing and manipulative — there's something about the way her eyes dart that makes you think she's pulling a fast one, spinning out lies to win Megan over to her side, though that's hardly the case. Knightley can be a marvelous actress, but she hits some wrong notes here, at times flashing a smile that looks too much like a misplaced grimace — it's as if she's just one take away from getting it right.

It's the smaller performances that really shine: As Annika's best friend, Kaitlyn Dever (who had a small role in last year's The Spectacular Now, as well as a recurring part on Justified) throws off naughty sparks — she's a cherubic wisecracker, sort of a post-millennial Dead End Kid. And Gretchen Mol, whose career never quite gained the momentum it should have, especially after her stunning turn in Mary Harron's 2005 The Notorious Bettie Page, gets just one small, quiet scene, but she's terrific in it. She plays Bethany, Annika's runaway mom, a woman who left her daughter to pursue big dreams that never quite materialized. When Megan drives Annika to Bethany's house for a surprise visit, this radiant but somehow disappointed-looking woman can't, at first, bring herself to face her daughter — her all-too-readable aura is a mix of shame, disquiet and curiosity about the child she left behind. “If you treat somebody badly enough, you start assuming they'll be happy to let you go,” she explains to Megan.

But Megan — who, conveniently, got her degree in marital and family counseling — intervenes, and Bethany comes around. She's been working as a lingerie model, doing catalog work, and the companies she works for give her lots of free stuff. Would Annika like some of it? She brings out a bagful of bras and panties and holds up one or two delicate little nothings for Annika's approval. It's the wrong thing to do, a clumsy way of building a mother-daughter bridge, yet it's the only thing to do. Mol infuses this nicely written scene with so much cautious sweetness that you believe every second of it. Bethany's daughter may be a stranger to her, but there's some hope the gap can be narrowed. A little lace and some Lycra aren't a bad place to start.

LAGGIES | Directed by Lynn Shelton | Written by Andrea Seigel | A24 | Landmark, ArcLight Hollywood

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