The first lines of dialogue spoken in Jason Yu’s clever horror-thriller Sleep (Jam) is “Someone’s inside.” These two words are spoken by Hyeon-soo (Lee Sun-kyun), a young husband who is apparently talking in his sleep to his pregnant wife, Soo-jin (Jung Yu-mi). Hyeon-soo is an actor, and when Soo-jin tells him about it the next day, he explains that it must have been a line of dialogue from a script. But, Soo-jin isn’t so sure, and her fears appear to be confirmed when Hyeon-soo begins acting stranger and stranger while asleep. It is as if he turns into someone else—someone violent, dangerous, vulgar—and then has no memory of it the next morning. Is he haunted, possessed, or simply suffering from some kind of sleep disorder?

If you have watched horror movies, you know that this is a classic duality that the genre frequently treads, with supernatural events tormenting characters who then turn to medicine and science for answers. The doctors and researchers, with their theories and tests and rational explanations almost always turn out to be wrong—sometimes terribly wrong—as the horror genre rests on the inexplicable and the mysterious. The second that the horrors can be rationalized, they lose their power to disturb and disrupt.

Writer/director Jason Yu, who previously worked as an assistant director on Bong Joon Ho’s Okja (2017) and is here making his feature debut, has internalized this schism between the irrational and the rational, and what makes Sleep such a smart riff on familiar material is that he initially plays directly into our expectations, but then halfway through turns the whole thing upside down. For half the film Yu leads us down a familiar path paved with the inadequacies of rational human understanding to explain supernatural horrors. But, then medicine and science seem to come through and the problem is apparently solved by the right medication. However, in the process, one character has become so consumed with the possibilities of supernatural explanation that they may very well have been destroyed and plan to take others down with them.

Much of the film unfolds in Hyeon-soo and Soo-jin’s small apartment, and Yu and cinematographer Tae-soo Kim do an excellent job of conveying both the mundane everydayness of their lived space and the constant dangers it poses to someone who becomes some(one)thing else when he goes to sleep. Kitchen knives, open windows, and household tools all become potential sources of danger, especially once the couple has a baby in the house. Yu takes us through all the processes Hyeon-soo and Soo-jin endure to make their space “safe” for Hyeon-soo’s sleep disturbances, which include padding all the furniture’s sharp corners and, at one point, putting a huge padlock on the bedroom door so he can’t come out. One of the film’s most unnerving sequences finds Soo-jin and their baby cowering in the bathtub behind a locked door that Hyeon-soo, in one of his frightful midnight manifestations, wants to knock down. The film’s horror and suspense play even better because they also reflect the normal anxieties of any marital relationship and the struggles of facing difficulties together. Sleep, after all, is the time when we are all the most vulnerable, and going to sleep next to someone is a fundamental act of faith. So, what happens when that person is no longer safe in the dead of night?

For the most part, Sleep works marvelously and takes us in some genuinely unexpected directions. It doesn’t quite reach Takashi Miike-Audition levels of unexpected violence, but let’s just say that a power drill plays a potentially horrifying role in the film’s third chapter. There is one fairly absurd scene near the end in which one character gives another character a PowerPoint presentation to explain what they think is going on, which undercuts the hellishness of the space Hyeon-soo and Soo-jin’s apartment has become. There are other absurdities, as well, but they otherwise work toward the film’s slow descent into what is either madness or horrible understanding, which is, in the end, the real root of horror.

Copyright © 2024 James Kendrick

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