Although she hopes to follow in her father's footsteps as a master constable, Luk Sap-Yee is an impulsive and idealistic constable whose skill and competence are often dismissed by her corrupt male peers. When Sui Tong-Lau, the newly appointed magistrate, arrives in Sap-Yee's city, they wind up working together to solve a number of unusual cases.

The Police Counter-Terrorism Unit (CTU) gathers intelligence to fight against terrorist attacks. Three beautiful female officers, Sam, Fa, and Bowie, who have different personalities, are outstanding members of this unit. Sam is a Chief Inspector in CTU. She is decisive and never mixes personal matters with work. Fa is good at martial arts and enthusiastic in her job. However, she can be very short-tempered. Bowie is a fresh graduate from the cadet school. She is very accurate at shooting, but she has no ambition at work. These three angels are friends and partners. In "Angels of Mission", they unite to fight terrorism.

A suspected criminal mastermind escapes from police custody, throwing the city into turmoil. With the police department now divided, rival police chiefs are forced to take their fight to the streets of Hong Kong with deadly consequences.

In the early 1970s, the Governor of Hong Kong decided to clean up the police force. The ICAC was established, whose operation branch was headed by Yim. Bong and Unicorn also joined the ICAC. Despite threats of violence and intimidation, they managed to bring about the downfall of the empire of graft.

Suki is a very devoted gambler. Whenever he goes to Macau, he buys a return ticket in advance, just in case he loses all his money. After breaking up with his girlfriend Cher, who couldn't bear his gambling anymore, Suki meets a girl called Princess Fragrance at a karaoke bar. They later meet again in Macau, both in the hands of a loan shark Brother Face, who threatens to kill them if they don't pay off their debts…

Laughing is formally a police undercover. However due to a drug trafficking case, Inspector Pan is hot on his trails. Before Laughing becomes a police undercover, he works under triad leader Yi. Yi treats Laughing as his own brother, however to protect his territory and illegal businesses, Yi instructed Laughing to join the police force and act as his undercover. Laughing is a high-flyer in the police academy. However he never got a chance to join the force because he is specially picked by Inspector Xian to be an undercover in the underworld syndicate. Hence Laughing becomes a “double-undercover”. Yi is happy that Laughing is allocated to the triad of his rival. To make his situation worse, Laughing falls in love with the triad leader’s sister, Karen. Justice, brotherhood and love, what will Laughing decide on? His decision will be a turning point in his life.