Sleep Review: Scary Sleepwalking Habits Haunt A Marriage In This Heartfelt Thriller [Fantastic Fest 2023]

Marriage is all about trust, about knowing the person sleeping next to you and knowing you're safe. But what happens when that trust is broken — when out of nowhere you realize you don't know this person, and they might hurt you one day?

That is the premise of "Sleep," the feature debut by Jason Yu, former assistant director to Bong Joon-ho, and a new voice in Korean horror cinema. Just like Wes Craven terrorized our dreams with "A Nightmare on Elm Street," Yu's "Sleep" haunts your waking moments. This is a claustrophobic and tense thriller that uses small locations and a small yet perfectly used cast to craft a thrilling and heartfelt love story disguised as a ghost story that definitely keeps you awake.

Soo-jin (Jung Yu-mi) and Hyun-su (Lee Sun-kyun) live in an apartment with paper-thin walls. He works as a successful actor, she is an office worker usually working late while her husband snores in bed. They're stressed out, but have a normal, functioning marriage. That is, until one night Hyun-su sits up while still asleep and utters two chilling words: "Someone's inside." This is enough to send chills down everyone's spine, including Soo-jin, who gets terrified and starts frantically looking around her apartment only to find ... nothing. 

Hyun-su is diagnosed with sleepwalking, a rather unpredictable condition that starts out kind of funny, then turns bizarre, and ultimately violent. Still, they are a unit, and they'll work through this, so Soo-jin stays vigilant, she locks doors, puts bells everywhere, and even buys a sleeping bag so Hyun-su can't easily get out of bed and attack their newborn — oh yeah, did I mention Soo-jin gives birth? If things couldn't be more complicated, Soo-jin's mother suggests a different solution: ghosts. 

"Sleep" works because of its cast, and thankfully it is excellent. A two-hander, Jung Yu-mi ("Train to Busan") and Lee Sun-kyun ("Parasite") have acted as a couple several times before and that familiarity turns into palpable chemistry here. But what makes the film so fun is seeing the two actors getting the chance to go big with their performances — especially the tremendous Jung Yu-mi. The more erratic Hyun-su's behavior is, the more unhinged Soo-jin becomes, until the final chapter of the film fully descends into horror.

What makes "Sleep" shine is the way it mixes the language of horror with a poignant story of domestic life and the struggles of marriage. "Together we can overcome anything," reads a plaque adorning the couple's living room wall, and it becomes both a rallying cry and a battlefield as things get heated between the two characters. Who walks away first from the relationship, and how far you're willing to accept bizarre behavior in the name of supporting your spouse become big questions in the film, and the script masterfully tackles them. Even as the events of the story get more concerning and extreme, you understand why the characters don't simply leave. 

Because there is horror. Jason Yu knows how to stage a tense thriller and gives "Sleep" a sense of claustrophobia, using the small size of the apartment and some inventive camera movements to slightly change the apartment throughout the film, showing how the characters are losing their grip by making them unfamiliar with the place they know best in the world. As for the ghost story, it plays a vital role best left unspoiled, but I'll say it pays off big time in the film's ambiguous ending.

/Film rating: 8 out of 10.