Something inside of all of us reacts instinctively to threats against our loved ones. It is an impulse stronger than that to protect ourselves, a fight or flight urge. The instinct is perhaps at its strongest when the threat is against our children.

In French language film Custody, Miriam Besson (Lea Drucker) reacts to her husband’s violence against her and her children by fleeing. When a judge awards joint custody of their young son to both parents, Miriam’s plans to rebuild their lives starts to derail. Husband Antoine (Denis Menochet) bullies his son Julien, desperately trying to get him to reveal the location of Miriam’s new flat, in the hope of a reconciliation. All the while, the couple’s daughter Josephine, old enough to make her own decision about where to live, avoids thoughts of her father and throws herself a little too deeply into her first romantic relationship.

There is another way this film could have gone, the way, admittedly, I was expecting it to. It seemed obvious that at least the first act would attempt to create conflict by playing the parents off one another. The audience would be manipulated, seeing both father and mother in good and bad lights before asking who, really, is to blame for this situation. Instead, writer/director Xavier Legrand reveals the antagonist immediately, showing us that the tension arises instead from watching Menochet’s Antoine descend further and further into anger and unpredictability. This is a masterful decision, only detracted from by development of Josephine’s romantic sub plot. Despite moments of magic, Josephine’s relationship with boyfriend Samuel is fundamentally less interesting than the main storyline, and seems unfinished.

There is brilliance in Legrand’s handling of the camera, but to call the style Hitchcockian does the film a disservice. The director knows exactly when to hold stillness, hinting that what is happening just out of shot is perhaps just as important as what can be seen. One shot in particular is breath-taking; a long unbroken take sweeping round the family at a party. No words can be discerned above the loud music, but the fluidity and micro-actions of the actors speak volumes. This is just one example typifying Legrand’s cinematic knowledge and excellence - it is no wonder that he was awarded a Silver Lion for his direction at Venice Film Festival last year.

Not one of the actors give anything less than their best. Menochet’s performance recalls Kathy Bates in Misery, or Glenn Close in Fatal Attraction, but his obsession, though just as violent, seems more grounded and realistic. His almost bipolar nature means that he is as terrifying when calm as when angry, because he could switch between the two at any second. As children Julien and Josephine, Thomas Gioria and Mathilde Auneveux hold their own, proving themselves through their fear, and strength in the face of it.

Miriam is given by far the least screen time of the four, but from the very start she is the surrogate for the audience. It is through her, and Drucker’s impressive commitment, that the truth in the terror is revealed, and then maximised. Whether this is a comment on human nature or a warning against domestic abuse is not clear, but the effect is staggering. Using Miriam as his pivotal driving force, Legrand deftly stokes the fire inside all of us: that animalistic instinct to protect.