Sleep (2023), originally titled Jam, is a masterfully tense Korean horror-thriller that transforms a domestic setting into a landscape of profound dread. The film follows Hyun-su and Soo-jin, a young expectant couple whose lives unravel when Hyun-su begins exhibiting bizarre and violent sleepwalking behaviors. What begins as concerning nocturnal episodes escalates into terrifying nightly rituals that threaten Soo-jin's safety and that of their unborn child. The central mystery—is this a psychological condition, a supernatural haunting, or something else entirely?—drives a nail-biting narrative that expertly balances intimate marital drama with genuine horror.

Director Jason Yu demonstrates remarkable control over atmosphere and pacing, using the confined apartment space to amplify claustrophobia and tension. The performances are utterly compelling; Lee Sun-kyun delivers a chilling, dual-natured portrayal of a loving husband by day and a monstrous sleeper by night, while Jung Yu-mi is phenomenal as the resilient, increasingly desperate wife fighting to protect her family. Their chemistry sells the heartbreaking reality of a relationship under supernatural siege.

Viewers should watch Sleep for its intelligent, character-driven approach to horror. It forgoes cheap jump scares for sustained psychological unease, exploring themes of parenthood, trust, and the unknown terrors that can invade the safest spaces. The 95-minute runtime is taut and relentless, culminating in a finale that is both shocking and emotionally resonant. For fans of elevated horror like The Babadook or Korean cinema's unique brand of thrillers, Sleep is an essential and unforgettable watch.