Detective Jiulong (played by Zhang Jin) is an elite detective in the Hong Kong police force. However, he is arbitrary and explosive in his actions, and is regarded as a "paranoid madman" by the police force. Jiulong was ordered to investigate a serial murder of young female police officers. After trying every possible means, he not only had no clues, but his policewoman fiancée Fang Ning (played by Stephy Tang) also disappeared unexpectedly during the arrest operation. Jiulong, who was struggling on the edge of love and pain, suddenly discovered that the serial murder of female police officers was only the first step. The murderer had a more bloody conspiracy, and he and his fiancée were also included in it. At this time, another female police officer was killed in Macau. This time the method of committing the crime was even more outrageous, but the murderer seemed to have deliberately left clues. Is it a dangerous trap or the dawn of revenge? Kowloon sets out without hesitation, and with the help of his good friend Wang Mengqi (Annie Liu) and international boxing champion Sin Lishan (Anderson The Spider Silva), he joins forces with Macau police superintendent Cao Zhide (Kevin Cheng) to conduct an investigation. The devil is one foot high, how high is the road! Before the blood debt is paid with blood, even if the last drop of blood is shed, we will never give up.