As the need to find a solution for the devastating impact of human activity on the environment grows ever more pressing, Dr Jørgen Asbørnsen makes a thrilling discovery in his Norwegian laboratory. It might just help save the planet: a technique that safely shrinks humans to Lilliputian size.

American every-couple Paul and Audrey Safranek (played by Matt Damon and Kristen Wiig) eke out a living in suburbia. Paul works as an empathetic occupational therapist at Omaha Steaks, having given up his chance to train as a surgeon to care for his elderly and infirm mother. After her death, they move into her small house and struggle to pay the bills.

When they meet friends whose lives have been vastly improved after miniaturisation, they check it out for themselves by visiting Leisureland, a domed community especially designed for downsized people. They’re shown tiny model mansions with luxury fittings, swimming pools and tennis courts; when they’re told that their $52,000 in savings will translate to $12 million there, with the bonus of the satisfaction of helping save the world, they decide to go ahead.

With Wiig topping the bill alongside Damon, it’s a bit of a shock when she’s written out early on. We’re shown Paul going through the procedure in riveting, believable and entertaining detail before he discovers his wife has changed her mind at the last minute. Divorce follows.

Giving this away may seem a plot-spoiler, but it’s in the trailer. More than that, though — this is nothing compared to the twists yet to come.

Suffice to say, the remaining rollercoaster ride of a movie includes Vietnamese dissident activist Ngoc Lan Tran (brilliantly played by Hong Chau), a playboy Russian smuggler of luxury goods (Christoph Waltz), a Norwegian utopian eco-village-cum-doomsday-cult and the discovery that the miniature utopia of Leisureland is not all it seems: just outside the protection of its dome lies a marginalised society that is worlds away from the luxurious and soulless mini-suburbia in which Paul finds himself.

While encapsulating the warmth of a tight-knit and diverse community, it also reveals that those less fortunate — the elderly, the infirm, the sick and the poor — are no better off by being five inches tall. It seems downsizing doesn’t eradicate the inequalities inherent in full-sized living.

With a sparkling multi-national cast, including brief cameos from the likes of Laura Dern, this film clocks in at over two hours. Some may feel the sprawl needs tighter editing, but it’s hard to see which segments could be sacrificed without losing the impact of the whole.

A film unlike any other, Downsizing triggers laughs, heartbreak and sobering reflection in equal measure. It delivers a vitally important message without proselytising, and is one not to be missed.

Downsizing opens in cinemas on Boxing Day, with an advance screening at the Moonlight Cinema in Botanic Park next Wednesday (December 20).