A serial murder case occurred in Linghai City, and criminal police Ji Fan joined forces with team leader Xiong Zhennan, forensic doctor Zhao Qingyan and others to investigate. However, the case was confusing and could not be solved. As the investigation deepened, Ji Fan gradually realized that the murderer seemed to be around. The seemingly simple serial murder case involved an old case 27 years ago. The truth buried by time was slowly revealed. The murderer was Ji Fan's father Ji Tingshan and brother Ji Ping, who lived with Ji Fan day and night, and Ji Ping took the responsibility of revenge for Ji Fan for 27 years. With Ji Tingshan's arrest, Ji Ping fled overseas with injuries. Ji Fan followed his trail to a European country, his second hometown where he grew up. While tracking down Ji Ping's whereabouts, Ji Fan also had to complete the undercover mission assigned by the organization, find out Mr. A, the manipulator behind the three major gang families, crack the secret of the gang's sacred object "Holy Grail", and was involved in the fight between gangs in a European country. With the assistance of the Czech police, Ji Fan finally found out the true identity of Mr. A, and Ji Ping's target was also Mr. A, and all this was inextricably linked to the past of the two.