On a stormy night, forensic pathologist Qi Yan receives the file on the long-sealed "Blue Moon Serial Murders," a case from twenty years ago. Then she spots her mother, missing for years, in a victim's photograph. Five women were arranged in artistic poses, each with a blue crescent mark on her neck. Every lead points to a private club that closed long ago: Blue Sea.
Following the clues to the club's former site, she meets Gu Zheng, a mysterious restaurant owner. He claims his father once invested in the club, yet shows an unusual interest in the case. As the investigation deepens, Qi Yan discovers that Gu Zheng's father had secret dealings with her mother. Meanwhile, the club's former manager, now confused and living in a nursing home, keeps repeating one crucial clue: "the man in the white suit."
When a copycat killer begins targeting the children of people connected to the case, Qi Yan becomes the next target. Kidnapping, threats, meticulously recreated crime scenes... The truth is far more brutal than anyone imagined. On the brink of life and death, she and Gu Zheng must confront their fathers' crimes. The bloody traces hidden beneath those white suits will finally be exposed beneath the blue moon.
