Xavier Legrand’s debut feature is, as its title might suggest, a study of a family in the aftermath of a custody decision, and one of the best depictions of marital separation and estrangement that I’ve seen on the big screen. It opens with a sustained custody hearing, in which Miriam Besson (Lea Drucker) and Antoine Besson (Denis Menochet) both make an appeal, through their respective lawyers, for custody of their children Julien (Thomas Gloria) and Josephine (Mathile Auveveux). With the exception of Miriam’s sister Joel (Jean-Marie Winling), and Miriam and Antoine’s respective parents, these are virtually the only characters in the film, which takes its cues from the taut claustrophobia of this opening sequence to exclude virtually everyone but the immediate Besson family from its purview. That said, claustrophobia is probably not quite the right term for the profound impersonality and procedural austerity of this sustained custody hearing, which plays more like a deposition drama than a legal drama, and could almost be staged as a play, were it not absolutely dependent on the parents, and their lawyers, sitting directly opposite the judge handling the case, and the camera’s frontal access to both. While Miriam alleges that Antoine is abusive, and Antoine insists that his character credentials are impeccable, it’s not entirely clear where the truth lies, and the judge eventually makes a default decision in her ruling to award the parents joint custody, and for the children to commute between them.

The film that ensues largely follows this process, and is suffused with an awkward tone that never quite congeals, yet that works perfectly to captire the dissonant, uneast and atonal atmosphere that settles over the Besson family in the immediate wake of the separation, and at the commencement of shared custody. In particular, Legrand beautifully captures the strange space between Miriam and Antoine as Julien commutes from one to the other (Josephine is unwilling, at this stage, to see her father), along with the way in which the family members who once filled out this space now rapidly recede from view. Whether they’re watching through windows or shutting the front door quickly to avoid any unnecessary eye contact, the texture of the family is replaced by a sudden and strange vacancy, with moments of crisis tending to constellate around what used to be the entry to their shared family home. So dispersed and dissociative does this become that Custody is almost entirely devoid of a tone, or an atmosphere, as if Legrand were asking us to participate in a family drama in which the family, as idea and institution, simply isn’t there.

Key to that atonality is the strange silence of the film – not only the silence between Julien and Josephine’s parents, but the silence of their new homes, both of which have been partly colonised by their grandparents, and both of which are inevitably contoured by the looming and ominous absence of the other parent. Time and again, Legrand brilliantly evokes the drabness of post-separation abodes as spaces that are largely constituted by their silences and voids, as well as the strange and vulnerable isolation of parents now rendered as single figures, and who thereby appear more conducive to bursting out into extremities of emotion that are utterly unprecedented to the children involved. Partly because Josephine is older and less invested in her father, much of that texture and atmosphere is anchored in Thomas Gloria’s almost wordless depiction of Julien, and the cognitive dissonance and self-alienation that ensues from Julien realising that his parents suddenly have nothing in common but him, and that they are prepared to turn all their attention to reminding him, in a myriad of little ways, that his perception of the other parent is and always has been erroneous. In a series of pivotal sequences, Legrand needs to do little more than train the camera on Gloria’s face, as Julien fights to reconcile the parents he once had with the individuals he now knows, in one of the best performances from a child actor in some time.

For all this emotional intensity, however, Custody never sheds the procedural austerity of the opening custody hearing, whose ambience is absorbed so completely into the Besson households that it is almost as if Julien and Josephine were present at the hearing themselves. Instead of organising his narrative in a conventionally linear way, Legrand works largely by elasticising and extending the space between the two parents, until every space that Julien inhabits feels transitory, even or especially his two new family homes. In particular, the film focuses on Julien’s walk from the front door to his father’s car, and the drive to and from his father’s house, as the two key nodes in this syntax of separation – and by about halfway through, it feels as if the entire film is taking place somewhere along this commute, thanks to a series of complications that include last-minute changes to the custody schedule, a sudden move of residence, and Antoine’s escalating volatility. In one especially distressing scene, Antoine drives Julien around until he reveals where Miriam now lives, only for Julien to escape the car, flee through a public housing estate, and finally return sheepishly to his father. Here, as elsewhere, Legrand really captures the push-and-pull of having separated parents, since Julien is clearly drawn to Antoine even when he is most repelled by him, which Antoine also seems to recognise and use to his own advantage.

While the film may be quite austere in its studied atonality, then, it never feels monotonous, partly because Legrand manages to include quite upbeat scenes in ways that just enhance the starkness of it all, like a dance track whose bassline has been turned up just a little too loud. That peaks in the penultimate scene, and the first and only burst of diegetic music in the film – a performance that Josephine gives at her birthday party, which has itself been a source of escalating tension and miscommunication between her parents. After such a silent and sombre film, this sustained musical sequence is almost unbearable in its abrasive awkwardness, like a burst of bright, harsh light after a film that has been uniformly muted and dim. That awkwardness is only enhanced by the fact of the song itself, since Josephine is not merely singing in English, but – somewhat improbably – singing Creedence Clearwater Revival, in a fusion of French pronunciation and a Southern-fried lexicon that raises the film’s alienating atmosphere to a fever pitch. Far from breaking or resolving the profound atonality of the film and family in any way, this rendition of “Proud Mary” catalyses the starkest confrontation between the parents so far, the first graphic depiction of domestic violence that we see in the film, and the first real confirmation that Antoine genuinely is a violent threat, and that the custody judge made the wrong decision.

That leads onto an extraordinary final sequence that, along with the custody hearing, bookends the drama with what amounts to a self-contained short film that could play equally well on its own terms. After returning from Josephine’s birthday party, Miriam and Julien return to her new apartment, only for Antoine to break in, try to break down the door, shoot his way through the door and then force his ex-wife and son to barricade themselves in the bathroom before the police finally arrive and take him, in turn, into custody. After such a sombre and introspective film, this final sequence is nothing short of traumatic, and yet part of its trauma comes from the way in which it retrospectively frames this outburst as an inevitability given the custody decision, and the way in which Miriam’s perspective was dismissed by the custody judge. In order to combine a moment of crisis while remaining true to the film as a whole in this way, Legrand exhibits a masterful command of space, time and tone, orchestrating the entire encounter – from the first distant sounds of Antoine outside to the last distant sounds of the police taking him away – with the dexterity, sensitivity and instinct for the right beat and pause of a master director.

At another time, or in another kind of film, this sequence – a father beating down the door to get to his wife and child – would feel almost invisible, or at least inevitable, as a trope, but part of the brilliance of Custody is the way it dissociates this scene from those expectations, rendering its inevitability all the more shocking and surprising in the process. In the most emphatic way possible, Legrand reveals that the custody ruling represents the default position of most films about separation, which is that the father is somehow always right, or at least that their insistence on their own fatherhood imbues them with a certain gravitas. Watching it, I realised that I had never seen a film about separation, or about the end of a marriage, that didn’t articulate it, in some fashion, as a tragedy of fatherhood, and the father as the main victim, even or especially if the father was the main culprit as well.

It’s that complication of the audience’s residual, and possibly unwilling, sympathy for the aggrieved father – and the automatic depiction of separation as a mode of emasculation – that this film challenges and skewers so brilliantly, instead affirming the protection and warmth of the maternal body, as Miriam takes Julien from his bed to the bath, where they lie down, under the instruction of the police, in order to avoid Antoine’s fire. Earlier in the film, when asked what he wants, Antoine simply replies “To know where my kids live,” and by the end of the film his whole role in the family – the whole family iself – has been commanded and co-opted by this paternal and patriarchal paranoia. Yet what makes Custody so unique is that it refuses to present this as a source of charisma, let alone pathos, ending as austerely as it began, and cutting to the credits once Antoine is led away, in one of the most deftly and dryly revisionist family dramas I have seen, and a quite daring debut.