In the shadowy evenings, where the stillness consumes the stars, a merciless criminal referred to as the X Killer resurfaces after years of quiet. He chooses to resume his hunt. Hong Li Wei, an exceptional detective and psychiatrist, experienced the loss of her younger brother at the hands of the X Killer and vowed to track him down. Yoon Xi Yuan, a keen detective whom no one dares to confront, remains silent, calculating, and concealing a profound secret that has the potential to transform her mundane existence into one filled with regret.