The exploration of the sometimes mysterious bond between a mother and her child is the kind of theme one might well expect to be best suited to straightforward melodrama but, ever the meddler with genre, Bong Joon-ho has crafted an engrossing detective-story thriller around the subject, a film which constantly defies the viewer’s expectations and offers both a moving portrayal of the power of the familial bond and a dark portrait of this link when pushed to its extremes. As well as being a play with familiar generic tropes, so too is his film a meditation on the importance of memory, set against the backdrop of a wider critique of male domination and female peripheralization in Korean society.

What characterized Bong’s previous two films, Memories of Murder (2003) and The Host (2006), was an obviously withering contempt for the patriarchal authorities contemporary to the periods in which they were set. In the former film, based on a real-life series of incidents in the late 1980s, a bungling police investigative team fail to catch a serial killer, while in the latter, the present-day residents of Seoul find themselves at the mercy of both their own paranoid government and the decidedly more gung-ho US authorities in the wake of an attack on the city by a gargantuan monster. In both films, it is the ordinary people who are made to suffer because of, or be scapegoats for, their public officials’ inadequacies.

Mother apparently continues this thematic concern by focusing on an unnamed mother’s struggle to clear her son Do-joon’s name after he is, she firmly believes, wrongly incarcerated and made an easy scapegoat for the brutal murder of a young schoolgirl. In trying to prove his innocence we see her comes up against over-worked detectives, violent police interrogators and – worst of all – her well-paid lawyer who turns out to be more concerned with scoffing buffets and drunkenly cavorting with escorts rather than helping her champion her son’s case.

The film is almost exclusively viewed from the point of view of Do-joon’s mother, and we are quickly inclined to feel sympathy for her when, in film’s first scene after the opening titles, we witness her cutting her finger with a large slicing machine while she is paying more attention to her son’s safety than her own. When Do-joon is hit by a passing car, the aggressive Jin-tae leads him to seek revenge on the driver at the local golf course, where we learn that Do-joon is mentally slow, forgetful and easily led by his more impulsive friend. Indeed, we see that while Jin-tae is capable of sporadic acts of violence, his meek friend is unable even to kick a car’s wing mirror without coming off the worst in the act.

Do-joon’s mother is, as any parent would be, concerned that her good-natured son continues to keep company with this ‘bad seed’, but their maternal relationship also seems at best off-kilter, and at worst positively unhealthy: though he is 27 years old, she still over-dotes on him as if he were an infant, and the virginal son still sleeps in his mother’s bed at night. In one tragi-comic scene she even feeds him ‘medicine’ while he stands in the street relieving himself against a wall; after he rushes off she tries to tidy up after him, scraping the urine away with her foot, and covering the spot with a nearby piece of metal.

The odd dynamic between mother and son seems strange but at this stage somewhat benign and as if it is being played for laughs, and when the harmless but distinctly un-savvy Do-joon gets hauled in by the police and roughed up by their interrogator in order to sign a confession, we naturally side with the mother in protesting his innocence, as well as suspecting Jin-Tae’s possible guilt. It is here that Mother shifts into a familiar detective-story mode, with the titular protagonist seeking clues to uncover the identity of the real killer, motivated both by her love (however strange) for her son and the apparent inability or unwillingness of the official channels of law enforcement to look beyond the circumstantial evidence of the case.

This is how the story appears to want to unfold as it settles down, and there is a sense of a return to his previous films’ concerns with the powerless oppressed struggling in the face of an uncaring bureaucracy. Our identification with the mother and her struggle has been uncomplicated, resting on easily identifiable premises: a vulnerable, elderly woman struggling against uncaring authorities to prove her mild-mannered son innocent and to turn suspicion towards his violent friend. Yet almost as soon as her own investigation begins she appears to come up against a dead end, one which turns at least one of these assumptions on its head. In classic detective-thriller tradition, and with more than a little hint of Twin Peaks, her sleuthing leads her to make some startling discoveries about her small town and she becomes embroiled in a much more sinister and potentially dangerous situation than she first had anticipated.

Mother‘s convoluted narrative about-turns not only maintain an admirable air of suspense for its 130 minute running time, but serve to undermine many of the assumptions and prejudices the viewer holds about the story and its characters. If Memories of Murder played on the tropes of the police procedural genre and The Host similarly toyed with the familiar mores of the family-drama-amidst-monster-attack movie, the film uses the setup of a detective-story to expose how the viewer becomes emotionally complicit with the depths of its main character’s moral elasticity without even realizing it – until, that is, it is too late. The beating heart of Bong’s film is a dark, twisted one which, as well as showing how familial bonds can be an empowering, all-conquering force for good, they are the same ones which can drive people to go too far. Nevertheless, lead actress Kim Hye-ja, familiar to Korean audiences for playing more placid matriarchs, conjures up a mesmerizing central performance as a quiet, subservient elderly mother steeled by her resolve to free her son, and it is hard not to be swept along by this woman’s sheer determination.

The film’s feminine title underlines the fact that there is a large focus on the cultural and social divide between the genders, and though the subject of female subjugation is not broached explicitly, it is one which is ever-present in the background. If men are not alternately portrayed as bullying, incompetent, pathetic, money-grabbing, self-serving, violent, whimsical or sexually rapacious creatures then, as in the case of the fathers of both Do-joon and murdered schoolgirl Moon Ah-jung, they are absent entirely. The question of Do-joon’s father is never raised, and at one stage his mother even suggests to one of her acupuncture clients that it was ‘medicine’ which made her pregnant with her son. By contrast, women are the efficient workers, the gossips who know what is happening in the community, the victims of bullying, taken advantage of sexually, or at the extremes are driven to drink or attempted suicide. The mourners at Moon Ah-jung’s wake are almost exclusively female.

Do-joon’s memory – or lack thereof – serves not merely as a device to initiate and maintain the central mystery plot, but also as a metaphor for his essential unknowability to his mother, regardless of how close their relationship is; to what extent his amnesia is selective by choice or otherwise is never made explicit, which leaves us as much in the dark as she is. One dramatic revelation about their past, however, offers some clue as to its cause, as well as suggesting that one thing he may not be able to remember is something that she chooses advantageously not to remind him of. It also serves to cast in darker hues both her character and her apparently unselfish servitude to him. By the end, we are left to guess the extent to which Do-joon is able to piece together what his mother has done; she, however, makes sure she takes steps never to remember, and the film’s memorable final shot serves as a poignant recapitulation of its equally striking first.

The film’s emotional zenith comes when the mother is called upon to visit JT, an adolescent with Downs’ Syndrome who has been captured after escaping from the sanitorium. She simply asks him if he has any parents, a mother? His negative reply causes her to break down – but is it entirely out of pity for him? Her relationship with her son may have empowered her to go to extraordinary, almost unthinkable lengths to save him, but as much as this moment comes as catharsis it also serves to remind her of the horrors she has witnessed too. All in the journey of a mother, though, one in which the ability to forget may well be as important as that to remember.

Mother is released on DVD on 20 September by Optimum Releasing.