On a rainy night, forensic doctor Qi Yan took over the "Blue Moon Serial Murder Case" file that had been lying dormant for twenty years, but saw his mother who had been missing for many years in the victim's photo. Five women were placed in artistic poses, with blue crescent marks on their necks, and all clues pointed to a long-closed private club - Blue Ocean.
When she followed the clues and found the old location of the club, she met the mysterious restaurant owner Gu Zheng. He claimed that his father had been an investor in the club, but he showed unusual concern for the case. As the investigation deepened, Qi Yan discovered that Gu Zheng's father had secret contacts with his mother, and the unconscious club manager in the nursing home kept repeating the key clue of "the man in the white suit".
When the copycat killer began to commit crimes against the children of those involved, Qi Yan became the next target. Kidnapping, threats, carefully replicated crime scenes... The truth is far crueler than imagined. On the verge of life and death, she and Gu Zheng had to face the sins of their fathers - those bloody sins covered by white suits would eventually reveal their true colors under the blue moon.
