Sleep, now on Hulu, is a terrifying movie rooted firmly in the real world

The notion that all the best horror is deeply rooted in reality is certainly debatable. After all, sometimes it’s the alienness of a horror movie that gives it power, forcing us to fit its strangeness into our everyday lives in order to better explain the mysteries of both. But if there’s any truth to the aphorism at all, then Sleep, one of last year’s most underrated horror movies and a new arrival on Hulu, seems like the perfect argument for it.

Sleep follows a young couple just on the verge of having their first child. One night, Soo-jin (Jung Yu-mi) wakes up to find her husband, Hyeon-soo (the late Lee Sun-kyun), sitting up on their bed and muttering a phrase. While she attempts to understand him, she quickly realizes that he’s suddenly, out of the blue, started to sleepwalk. After a few nights of the couple simply trying to ignore Hyeon-soo’s new affliction, his somnambulistic episodes start turning dangerous and violent – scratching his own cheeks until they pour blood, or nearly throwing himself out a two-story window.

Throughout, Sleep is downright studious in its commitment to presenting all of this logically and with thorough explanation. As one character in the movie eventually points out, the earliest versions of Hyeon-soo’s sleepwalking aren’t just obvious to the viewer, they’re literally textbook, which the movie continues to make clear with each horrifying escalation.

All this leads up to an early encounter with a doctor who essentially just shrugs and explains that sleepwalking can just be like that, and medically we don’t really understand it or how to cure it. It’s a revelation that, thanks to Sleep’s careful realism up to this point, is allowed to feel as tactile and terrifying as another movie revealing that an ancient demon was real or that the killer cut the phone lines: it’s horrifying and hopeless in a way that feels impossible. All they can do is give it time.

Shortly after that visit, the couple has their baby, and Hyeon-soo’s condition starts to feel like a time bomb. First-time feature director Jason Yu, a mentee of Bong Joon-ho who also wrote the film, starts setting more and more of the movie at night, giving us shadowy glimpses of Hyeon-soon ambling about, or keeping the camera tight on Soo-jin’s terrified face while she listens to her husband wander their apartment behind a locked door. Each night feels like it brings a completely new type of terror, and gives us a sense that, just like the characters, we’re slowly losing our grip on reality, slipping sleeplessly into a state of constant terror and waking nightmare.

But the real payoff to the movie’s careful commitment to reality, and insistence that we too feel the characters’ weariness, comes when Soo-jin’s mother brings in a shaman as a last ditch effort to cure Hyeon-soo. Sure, it seems ridiculous at first, but the more the doctors simply suggest the couple wait out Hyeon-soo’s dangerous nights, the more the supernatural seems like a more compelling answer than those provided by medicine’s nascent understanding of sleep.

All this is a delicate tight-rope act to walk that Yu does wonderfully, thanks in part to the movie’s seldom used and genuinely shocking sense of humor, slowly bringing both the characters and the audience from carefully grounded realism to sheer desperation for answers, no matter where they come from. If there’s any one complaint to be had about the movie, it’s that it could have spent even more time with its characters immersed in the shamanistic quest for answers, but considering how great the film’s climax is, it’s hard to have any real issues with Yu’s approach — particularly when he finally lets us start questioning what’s real and what isn’t.

It’s hardly a surprise to say that you wouldn’t want to experience something that happens in a horror movie. But Sleep’s commitment to suggesting that just about anyone could suddenly be struck with a partner developing a sleepwalking disorder just as their new child arrives is far more imaginably and relatably terrifying than just about any other movie from 2024. That’s not to say it’s necessarily the scariest, but it’s certainly the one most likely to keep you up at night.

Sleep is now streaming on Hulu. It is also available for digital rental or purchase on Apple TV.