Sometimes films are not what they seem. And so it goes with US indie gem My Old Ass, whose cheeky title and outlandish conceit give way to a surprisingly sensitive, emotionally impactful comedy drama about growing up. And those tuning in for its headliner, Aubrey Plaza, will find her in short supply; instead, the film acts as a cinematic launchpad for promising young star Maisy Stella (best known to date for TV’s Nashville).

It focuses on 18-year-old Elliott Labrant (Stella) as she prepares to depart the family’s cranberry farm and head off on her big college adventure, without fully appreciating what she’s leaving behind. Whilst tripping on mushrooms with some friends one night, Elliott encounters her 39-year-old self (a characteristically droll Plaza, positively dripping with life’s disappointments and residing in what sounds like a vaguely apocalyptic future). The pair remain in contact afterwards via telephone, with the older Elliott offering life advice, including a warning to steer well clear of a boy named Chad (Wednesday’s Percy Hynes White).

Despite the credulity-stretching concept, this is a remarkably well-judged effort from sophomore writer-director Megan Park (The Fallout), a warm and witty film with a lot to say about the importance of living life without fear and being allowed to make your own mistakes. The aptly named Stella is a star in the making, a radiant screen presence with natural comic timing. My Old Ass reaches some enlightened, hopeful and non-patronising conclusions during its tremendously touching climax, and is brimming with compassion for the poor, confused teenagers we once were.

My Old Ass is in cinemas from Friday 27 September.