Four and a half stars

Director Bong Joon-Ho

Starring Choi Woo-shik, Song Kang-ho

Rating MA15+

Running time 131 minutes

Verdict Worms its way under your skin

With all due respect to Tolstoy (Anna Karenina), all happy families are not alike.

The Kims might live in a cramped “semi-basement” — drunks regularly urinate in the alley they underlook — and their employment prospects are uniformly grim.

But they’re a resourceful, mutually supportive, exceptionally tight-knit bunch with a wicked sense of humour.

When the upstairs restaurant introduces a Wi-Fi password, Ki-woo (Choi Woo-shik) follows his father’s directions to “hold the phone high,” solving the immediate crisis by locating a faint signal in the far corner of the “mezzanine” toilet.

This enables the Kims to access their What’s App messages, and a contract job assembling pizza boxes. But things really start to look up when Ki-woo unexpectedly lands a tutoring job with the wealthy Park family.

Thanks to the superb forgery skills of his smart-as-a-whip sister, Ki-jung (Park So-dam), combined with his own self-effacing charm, Ki-woo wins over the bored, gullible Yeon-kyo (Jo Yeo-jeong) and her sheltered teenage daughter with relative ease.

The family’s indulged, disruptive young son provides an opening for Ki-jung, who presents herself as a respected art therapist.

Jobs for father Ki-taek (Song Kang-ho), as the Parks’ driver, and mother, Chung-sook (Jang Hye-jin), as the live-in housekeeper, follow.

Korean director Bong Joon-ho (The Host, Snowpiercer) implicates his audience in this set-up with as much dexterity as the Kims ensnare the Parks.

Having been won over by the underdog family’s cheeky street smarts, we’re on board as their behaviour becomes increasingly outrageous.

When Ki-jung entraps the Parks’ affable former driver by leaving her knickers under his seat, for example, it’s hard not to appreciate her quick thinking and audacity.

At one point in the film, the Park family’s patriarch (Lee Sun-kyun) observes that while Ki-taek regularly comes close to crossing the line, he never actually does.

Bong Joon-ho toys with this imaginary demarcation for much of the film.

In fact, it’s hard to pick exactly where humour becomes horror — especially because the filmmaker continues to move deftly back and forth between the two. But the Kims’ lack of sympathy for the Parks’ former housekeeper certainly transgresses any kind of moral code.

Parasite isn’t just a cautionary tale about class, privilege and greed — Bong Joon-ho is far too interesting a filmmaker for that — but it does offer some rich and nuanced observations on the subject.

The film, which won the top awards at the Cannes and Sydney Film Festivals this year, can also be appreciated as a ripping good yarn.

Opens Thursday