Seo-jin (Shin Min-A), a photographer slowly losing her eyesight due to a hereditary condition, discovers the body of her twin sister Seo-in (Shin Min-A), who had gone blind years earlier but built a successful career as a ceramic artist. While everyone believes her sister took her own life, Seo-jin suspects foul play. Haunted by cryptic artworks left behind in her sister's studio and the presence of an unidentified figure seen on the day of her death, she sets out to uncover the truth for herself. But as her vision continues to fade, she becomes the killer's next target. Detective Do-hyuk (Kim Nam-hee) becomes Seo-jin's eyes as they investigate the case together. Yet as the truth slowly comes into focus, both are drawn deeper into a mystery more disturbing than either could have imagined. Amid the darkness, a terrifying truth comes to light.