Red Thread follows a fanatic who, after suffering a violent headache, discovers a vertical eye emerging from his forehead. Soon, a series of gruesome murders, lurking spirits, and ghostly apparitions begin to infiltrate everyday life, while fears rooted in a haunting past resurface. What is the Red Thread, and how does it connect them all?

Detective Kien investigates a headless body found in a rural Vietnamese village during the Nguyen Dynasty. As supernatural elements emerge, he faces chilling twists in this 19th-century mystery.