Sleep aka Jam (South Korea 2023: Dir Jason Yu)

In Yu's clever and impeccably acted debut feature, successful actor Hyun-su (Lee Sun-kyun) and his heavily pregnant estate agent wife Soo-jin (Jung Yu-mi) live happily in their small apartment, eagerly awaiting their new bundle of joy.

Their life becomes disrupted when Hyun-su begins showing signs of sleep disturbance, deeply scratching his face during the night, the wounds resulting in him losing the acting role to which he aspired. Added to this their downstairs neighbour, somewhat bafflingly, complains about excess noise from the couple's flat.

Hyun-Su's symptoms get worse; Soo-jin wakes up one night to find her somnambulous husband eating raw meat, eggs and fish straight from the fridge, narrowly stopping him throwing himself out of the window. Even more horrifyingly, one morning she finds their cute little Pomeranian dog in the freezer.

While her husband seeks a medical solution for his condition, which is diagnosed as REM sleep behaviour disorder - and medicated accordingly - things don't seem to be improving. On the advice of her mother, and concerned about the potential safety of their now just born baby, Soo-jin consults a shaman, and from there a supernatural element creeps into proceedings; the battle for Hyun-Su's recovery - and indeed soul - has begun.

The genius of Sleep is its transformation from light comedy to domestic drama to, well, something a lot darker, achieved effortlessly and, for the most part, in the confines of the couple's modest apartment. Much of the credit for this is due to the perfect casting of Sun-kyun and Yu-mi; this is, essentially, a two hander requiring, by the end, a massive suspension of disbelief, which the pair effortlessly manage.

This is also a film which, in quite an extreme way, details the way in which cracks can appear in otherwise sound relationships. In other dramas the tensions here would arise from, perhaps, the change wrought by the arrival of a new baby. Sleep turns this on its head by those changes coming from an existing member of the household. Words contained on a plaque on the couple's wall remind them that, as a married couple, they are able to face problems together; but when the problem is outside of their control, watching their attempts to adhere to the message are both tragic and, on occasion, darkly humorous.

Yu's previous experience includes AD work on Bong Joon Ho's excellent 2017 movie Okja, and there's something of that director's humanity amid the fantastic - and of finding comedy in situations rather than dialogue - at work here. I look forward to seeing what he comes up with next.

Sleep is in UK cinemas from 12 July.