Sleep is a well-crafted horror film that delivers both genuine scares and an engaging, character-driven story. Foregrounded by Jung Yu-mi (Soo-jin) and Lee Sun-kyun’s (Hyun-su) amazing performances, the simple-yet-intriguing premise and intimate setting of the couple’s apartment create a creepy, increasingly claustrophobic atmosphere. The couple radiates warmth for each other, and their adoring relationship makes Hyun-su’s strange sleep condition even more unsettling as Soo-jin becomes more afraid and suspicious of her husband. Director Jason Yu skilfully plays with the tone, adding dark comedy to lighten the tension, but the tight pacing ensures the suspense never subsides for long.