No-one is having more fun with genre right now than the director Bong Joon-ho. You may remember the name from 2006's monster mash-up The Host, which pitted a dysfunctional family of misfits against a giant amphibian creature emerging from the Han river, but seasoned Bong-ites have been spreading the word since 2003's outstanding Memories of Murder, which took a melancholy tale of true-life serial-killing that shocked Korea, and added grace notes of crime-scene and interrogation-room knockabout: it kicked its characters up the backside, and then - once the laughs had subsided - left us feeling a lingering pain and sadness.
Trace elements of this latter film resurface in Bong's latest, Mother, which sets out as an offbeat detective story about a provincial simpleton framed for the murder of a young girl he drunkenly followed part of his way home one night. The police are convinced the murder was the accused's way of proving himself anything other than nice-but-dim; the only person who believes in his innocence - who refuses to give up on him, even as his own lawyer retreats to a nearby karaoke bar, clutching a plea bargain - is his dear Mum. She's sure her boy couldn't have done it, because it's she who was sleeping next to him (albeit on the other side of the covers) that evening. Now that's an alibi.
It could have been a fairly distasteful one, too, adding another mother to that pantheon of creepily possessive movie matriarchs that includes Mrs. Bates and Mommie Dearest, and even Debbie Reynolds, fussing over Albert Brooks in the American comedy of the same name. Yet Bong rather admires this momma's pluck and resilience, her willingness to go to places nobody else will to plead her son's case: to a wake for the deceased, for example, where the dead girl's own mother is pointedly shown checking her reflection in a framed portrait of her daughter; or into the heart of an all-male squadroom, dispensing treats to all and sundry as she goes; or - when push comes to shove - into a suspected murderer's lair armed only with a set of acupuncture needles.
The mother is driven by her lack of vanity, a kind of blithe, imperious selflessness, a desire to help out (some might say interfere) wherever possible - heightened versions of characteristics displayed by good-to-great mothers everywhere. The real devilish joy lies in the detail Bong embroiders into this yarn: the detective who, William Tell-like, practises his obscure martial art with the aid of a desk drawer full of apples, the never-explained sex game observed from the closet of one suspect (very Blue Velvet, this) that involves the participants breaking words down into their constituent syllables. Bong is doing much the same himself: dismantling anything remotely familiar, and reassembling it in ways that seem fresh, appealingly strange - heck, even stimulating, if it's the sort of thing that floats your boat.
Scarcely a moment in Mother is wasted - which makes it a more compact proposition than the expansive, CG-enhanced The Host - and it's cast superbly, in such a way as to finesse any bumps or joins from scene to scene. As the ma in question, Kim Hye-ja proves an indelible combination of Miss Marple and habitual worrywort, fussing over her offspring even as he lets rip with a stream of urine at a bus stop, and managing against all the odds to retain some degree of sympathy even after the revelation mother dear tried to snuff the lad out with insecticide at an early age. (To be entirely fair, it was simply to generate further motivation to top herself - and she does go on to express remorse for not using a stronger brand to complete the task.)
These two, we gather, are in it together, and Bong recognises as much by isolating the pair of them within the widescreen frame at various points, quietly suggesting the forces against them in a generally unjust, macho society. In the extraordinary closing act, easily one of the strongest this year, the mother finally crosses a line, as we're offered a whole new angle on events - the sound you can hear coming from just off-camera that of Bong giggling hugely as he overturns our expectations once again. It's this glee - infectious, if the final sequence of onscreen revelry is anything to go by - that keeps Mother from growing stale or predictable: the glee of a filmmaker who, like Hitchcock fifty years before him, has realised just how far off-course it might be possible to venture with the idea of a boy's best friend.
Mother is out now on DVD.