The drama is set from the late 1930s Republic of China to the early 1940s Second Sino-Japanese War, centering on the conflicts between an influential triad family, who manages a successful opium production business in Guangzhou, and the city's police force.
The two protagonists, drug lord Miss Kau (Sheren Tang) and criminal investigation team captain Lau Sing (Wayne Lai), begin to share a complicated relationship after experiencing various political and emotional setbacks.
In 1936, villager Tong Kat, nicknamed "Spareribs" (Pierre Ngo) arrives in Guangzhou after gaining a spot in Lau Sing's (Wayne Lai) criminal investigation team.
His grandmother sold all her land to the police superintendent, the superior to Leung Fei-fan (Evergreen Mak), in order for him to gain entry and he promises to repay her and be a good policeman.
Meanwhile, drug lord Cheng Long-kwan (Elliot Ngok) successfully secures a smoking license from the government and opens up a public opium den.
Spareribs finally becomes friends with Sing and moves into the flat he shares with the police team at Chu Lung Lane, owned by Mrs. Yeung (Kara Wai).
Long Kwan puts Kau Mui in charge of Choi Hing's case and she lets him go publicly, much to the dismay of Tung Tai's men and the rest of the Cheng family.
Kau Mui "executes" Choi Hing in front of Long Kwan and Lau Sing hears the gunshot, thinking she reneged on her promise.
Everybody is curious as to how Kau Mui could follow Lau Sing's fabricated story about Choi Hing so quickly and laughs saying they have similar brainwaves and good chemistry.
Long Hei and Tai Fung bring him to the entrance of a carabet dance club, where they remind him of the old Siu Hong who had killed a gang rival in cold blood at the same spot.
Inspired, Siu Hong gathers all the gang members and assigns them a secret task: to find out if Kau Mui is really Long Kwan’s daughter and his sister.
Spareribs's grandmother comes for a visit but dies and Lau Sing helps pay the funeral expenses, eventually driving the restaurant to bankruptcy.
No matter how hard Kau Mui tries to help her quit, she ends up in a vegetative state due to smoke inhalation after she was caught in a fire at an opium den.
Long Hung (Kwok Fung) arrives from Shanghai, and praises Kau Mui for having foresight to shut down the opium dens in order to avoid possible wartime damage and losses.
Lau Sing and his team go to help the wounded but an air raid strikes, the women back at Chu Lung Lane grow worried.
Kau Mui delivers rice and other goods to Chu Lung Lane and Lau Sing gets the neighbourhood together for a final dinner together knowing that the Japanese army is about to occupy the city.
She receives a call from Hong Kong letting her know that Lan Heung is in her final stages and sends people out to find Lai Wah so she can speak to her mother on the phone one last time.
Kau Mui tells Lau Sing that the Japanese plans to send 500 orphans from Guangzhou to the harsh conditions in the northeast and if she continues opening opium dens, she can get enough exit permits for them to safely leave for Hong Kong or Macau.
Lau Sing reminds Kau Mui to think of herself and her own reputation, as the entire city is calling her a traitor but she asks him if he has another way to save the children.
Kau Mui, not realizing the mother and son already escaped, tries to negotiate with Fei Fan but he threatens her by recording her and asks for 100 permits which were supposed to go to orphan children.
Lau Sing waits for Kau Mui at Tung Tai and takes her to the church they always meet at to help her kick her addiction but he fails to hold her back.
Lau Sing goes to Long Kwan and lectures him of being a narcissist, only caring about his own reputation while his daughter takes all the shame of being a traitor in the public eye.
She cooks up a story saying that she and Lau Sing are in a relationship but Tetsuya tells her there's nothing else he can do since it is known the Japanese Army would rather mistakenly kill innocent suspects than accidentally release a guerrilla.
Lau Sing and the public plead for Spareribs to be released after sharing the horrific crimes Tetsuya has committed and the Chinese soldiers turn a blind eye.
Kau Mui helps Long Hei and Siu Hong by telling her father to let them have a quarter of the family assets and allowing them to leave in peace.
Long Hei returns and tells Kau Mui that Tai Fung died escaping the civil war, as the Communist government took control of Shanghai.
With the Nationalists unable to hold onto China for more than a few weeks, all public servants including Lau Sing, Spareribs and his police colleagues are ordered to evacuate to Taiwan.
After 30 years, in 1979, China began its reform and opening process, and Kau Mui can finally make a trip to Guangzhou to find Lau Sing.
When she arrives, Kau Mui reunited with almost everyone at Chu Lung Lane (with the exception of Wong Luk's wife, who died at some unspecified point in time).
After the Cultural Revolution, he was allowed to return to Guangzhou, and in recognition of his still-excellent sharpshooting skills, he was appointed as principal of a police training academy in Foshan.