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When she’s not squeezing into corsets or chunky cardigans, as she does in this month’s The Imitation Game , Keira Knightley’s carving a niche for herself over the pond in low-budget crowd-pleasers like Seeking A Friend For The End Of The World and this year’s music industry romance Begin Again . Keira’s latest indie effort sees her team up with director Lynn Shelton ( Humpday ) for this quarter-life crisis comedy.

Known as Laggies in the US, Say When is about late-twenties malaise. A Washington suburbanite, Knightley’s Megan is 10 years on from graduating high school, aimlessly floating into adulthood with no career prospects while her friends (including Ellie Kemper’s oh-so-annoying bestie) have their lives in perfect working order. When her boyfriend (Mark Webber) proposes, rather than offer a lifeline, it sends her into a panic – not helped by the fact she’s just accidentally caught her father (Jeff Garlin) in a compromising clinch. So what does she do? Pretend she’s off on a retreat, and hunker down for a week with Annika (Chloë Grace Moretz), a teenager she befriended in a parking lot who lives with her easygoing dad (Sam Rockwell).

The intergenerational friendship soon becomes interdependent, with Megan acting as big sister to Annika, whose own estrangement from her mother (Gretchen Mol) has left her with issues. A coming-of-ager, then – and what follows never really surprises: the beats, reveals and punchlines arrive as if precision timetabled.

Yet, perhaps thanks to Shelton’s skills at working in a semi-improvisational style, Say When never feels overly contrived. There’s a freewheeling authenticity to the way the characters interact, one that’ll leave you with a smile of recognition on your face. Led by a fabulously fragile Knightley, Say When still has the capacity to charm, even if it won’t ever fully bowl you over.