A Macao police officer's bachelor life is interrupted by the daughter he never knew he fathered.

The tenants of a seedy rooming house in Hong Kong think they're seeing a vengeful ghost when a strange girl arrives claiming to be the twin sister of a missing occupant. Wracked by guilt, they begin to die one by one, and the detective investigating their apparent suicides discovers that whatever karma people give out comes back to them... twofold.

The Crime Investigation Department is assigned to protect a princess-consort coming from the Republic of Puerto Risi. They arrange a fantastic trip to introduce the princess-consort to Hong Kong, but a big crisis looms on the horizon.

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.