Sleep: an unnerving investigation into the fragility of marital trust

Combining drollness and dread, writer-director Jason Yu offers a subtly unnerving exploration of marriage in Sleep. The mix of tones is characteristically Korean, but the film is pleasingly individual in the way it alternates light-hearted domestic comedy with unsettling nocturnal horror. The contrast between charming, loving husband Hyun-su and his sinister night-time alter ego evocatively hints at the strange and mysterious layers that lie under the familiar. The words he utters in his first sleepwalking episode are chilling: “Someone’s inside.” It is as though a dark force has infiltrated the home space and is corrupting its wholesomeness.

Whether that force is external or comes from within the couple remains ambiguous for most of the film. Initially, the focus is on the husband but, shrewdly, the film casts both spouses in turn as dangers to the family. As they resort to drastic measures to contain Hyun-su’s outlandish somnambulism, the domestic threat shifts from husband to wife: prepared to go to extreme lengths to protect her newborn baby, Soo-jin becomes an unpredictably fearsome figure. In this rapid disintegration of marital trust, the fragility of familial normality is keenly conveyed.

In fact, Soo-jin’s feverish insistence on sticking together no matter what proves one of the most damaging influences on the family. At the core of the story is the couple’s motto, “Together we can overcome anything”, which hangs on the wall of their cosy apartment. When Hyun-su, rather sensibly, proposes to sleep at a nearby inn after their baby is born, to shield his daughter from his volatile behaviour, Soo-jin passionately refuses, seeing her husband’s solution as “giving up”. She would rather sacrifice the sanity and safety of her husband and child to toxic togetherness.

Sadly, the film shies away from developing that idea fully. There is a sense that it does not quite know where to go with the themes it has so intriguingly set up. The final part feels rushed and uncontrolled, with odd ellipses and narrative choices.

One key revelation, which uncovers an important side of Soo-jin’s character, and which should have a major impact on the couple’s relationship, is minimised by the way it is presented, its dramatic potential left unmined. Despite some striking visual elements, the sense of unease built up in the first two parts fizzles out. Considering the disturbing behaviour of the couple in this crisis, it seems almost incongruous that the film should choose to reaffirm marital solidarity in an underwhelming and rather sentimental finale.

► Sleep is in UK cinemas starting from 12 July