Story: Soo-jin (Jung Yu-mi) has a respectable office job and Hyun-soo (Lee Sun-kyun) is trying to have his breakthrough as an actor. The newlyweds are extremely happy, and a baby is also on the way. However, one night, Hyun-soo suddenly starts talking in his sleep. What he says disturbs Soo-jin, but after it becomes clear that it is a line from a script, everything seems to be fine again. Until Hyun-soo scratches himself bloody in the middle of the night. In another night, he eats raw meat from the fridge. The two go to a doctor and it is quickly discovered that Hyun-soo's REM phase is abnormal. He is given some medication and a few tips about what to do at home, but it will take a while before he can expect some improvement. In the meantime, Soo-jin becomes more and more anxious because her husband is becoming increasingly violent when he sleepwalks, and she is afraid that he might hurt her baby in the future. After the baby is born and they are still trying to solve the problem, Soo-jin's mother also gets involved and wants to call in a shaman. She is convinced that a ghost is possessing Hyun-soo at night. But as long as long as Soo-jin can't figure out who wants to take her husband's place, the shaman can't help either...
Review: It's not easy to pinpoint exactly why "Sleep" can come across as a black comedy at first and even during the further course of the story. It's not like "Sleep" doesn't take itself seriously as a horror movie. It's more like the couple's relationship often adds a self-ironic touch to some aspects of the movie. And yet the love between the two is clearly the plot's center. The big question is also how far you would go as a couple to get rid of problems and save your marriage. Still, all this develops into an extremely effective horror story, in which physical and mental exhaustion or rather lack of sleep drive the protagonists to extremes. The plausible escalation while the couple tries to hold on to their love allows "Sleep" to show a depth that you rarely get to see in horror movies. And particularly because this flick is anything but cheap when it comes to its story, it can be called one of the best genre works from South Korea of recent years.
The horror elements themselves can't necessarily be described as original, but the strengths of the genre are used brilliantly. On the one hand, there is the dense atmosphere, which is further facilitated by the fact that the movie mainly takes place in an apartment, on the other hand, there is the fact that the horror doesn't show us much, but instead creates fear by hinting at things that might be. This is most impressively shown in the scene in which Soo-jin panicky searches for her baby in the apartment, without going further into detail. The growing paranoia makes the problem of the sleepwalker, whose actions are unpredictable at night, fade into the background when Soo-jin starts becoming a nervous wreck. At the latest when the shaman gets involved, "Sleep" doesn't simply make us doubt whether there is actually something strange going on or the horror might be explained rationally, but we are constantly forced to move between the two options until we don't know what to believe anymore.
The compact 95 minutes are divided into three chapters, between which there are small time jumps, but which also glue us to the screen with increasing intensity. Ultimately, the apartment really gets claustrophobic and the supernatural aspect comes to the fore more and more, even if you could still explain things purely rationally. The fact that the focus is exclusively on the married couple and there are only a few supporting roles also contributes to the constricting feeling. Lee Sun-kyun ("Kingmaker") does a solid job, but Jung Yu-mi ("Train to Busan") is allowed to show more facets as her character undergoes a bigger change. In the last third of the movie her performance is crucial to drive up the suspense level. So, in terms of acting, we get a good foundation, but the real reason why "Sleep" is such a successful genre work is the dense direction and the gripping images.
Even though director Yoo Jae-sun (aka Jason Yu) delivers his debut work here, he has already worked on "Okja" alongside Bong Joon-ho, and you can see his experience. It's not only the dark humor, which comes through in his imagery and reminds you a little bit of Bong too, that has to be mentioned in a positive sense, but also the overall successful direction including some tricks that never let us know for sure whether there are really supernatural powers at work or not. The budget probably wasn't very high either, but it never seems that way, and towards the end we even get an impressively "redesigned" apartment. It is also praiseworthy that the movie avoids having any longueurs. The movie is just as long as it needs to be, and there is no unnecessary epilogue. The ending is also extremely satisfying. It may seem a little open at first, but everyone will be convinced that their own interpretation of the events is the right one.
Paradoxically, all these positive things also lead to the point of criticism that "Sleep" is ultimately just a horror movie. Albeit a pretty good one. This means that you repeatedly get the impression that there could be more to it than meets the eye. We get some hints of social criticism, and "Sleep" is written too cleverly to just be a horror movie. But this approach is not pursued any further, and so all that's left is a genre entry, which is perhaps the best since "The Wailing" but somehow could have been more, if the director had been a little more courageous. However, that shouldn't and can't deny the fact that "Sleep" is a wonderfully dense horror thriller that offers great moments and is gripping at all times. Measured against its genre, this movie is above all else surprisingly innovative and therefore gets a clear recommendation.