When the Blood Moon rises, the boundaries between reality and nightmare disappear... Four friends-Park Yuna, Doyeon, Ellie Kim, and Kim Chan-woo-have always been outcasts at school. But they share a secret that binds them stronger than any friendship: a hidden basement where they investigate supernatural phenomena and mysteries best left undiscovered. One night, Yuna has a terrifying dream-a headless woman in black warns her: "The Blood Moon will rise soon." She wakes up in a cold sweat but dismisses it... until she encounters the very same ghost in the school hallway. That same night, her life comes to a mysterious and tragic end. The official reports claim she simply tripped and fell, but her friends refuse to believe it. The security footage shows one thing, while the wounds on Yuna's body tell another story. As they begin their own investigation, dark secrets about the school-and their own past-come to light. Every step brings them closer to the truth, but someone is working against them. Someone among them may be a traitor... The Blood Moon has already risen. And now, there is no turning back.