After the hot-tempered police detective Fei messes up yet another operation, he is transferred to a fictional department that houses all the useless staff the force couldn’t sack. There he finds a new enemy in the mild-mannered desk officer Johnny, who loathes Fei’s disregard for discipline. But when Fei’s father and Johnny’s mother coincidentally become an item, the new brothers must somehow learn to cohabit under the same roof.

Sit Ho Ching used to be an everyday white-collar worker who had no ambition and no plans for his future. Everything went smoothly until one day, when his boss set him up and his girlfriend cheated on him, he suddenly became a jobless single man, which made him rethink his past life of duties and routines. From then on, he decides to pursue wealth and fame by all means.

Kung (Eric Tsang) and Kin’s (Jacky Cheung) rivalry goes way back to the seventies when they fought over the same girl, who eventually became Kung’s wife (Anita Yuen). Now they run competing phone stores right across from each other on Mongkok’s busiest street, and stretch their minds trying to outdo each other with crazy promotions. There’s absolutely no mixing with the enemy in these parts – until Kung and Kin’s kids fall for each other! Further chaos breaks out when the landlord triples the rent of all the shop owners to force them out for redevelopment.

Laughing is judged guilty of murdering gang lord Michael So and is sentenced to life imprisonment. Locked up behind bars, he meets the seemingly benign inmate Fok Tin Yam, a university professor in criminal psychology who is jailed for drug possession. Highly intelligent and manipulative, Fok reveals the power of his mind games by effortlessly subduing the violent prison bully. He also deduces that Laughing is sent to the prison on an undercover mission to find out the rogue cops within the police force. The clues lead him to inmate Chit, a former sergeant from the Narcotics Bureau who has been suffering from a mental disorder. To unlock the critical information from the deranged man, Laughing must get the help of Fok, but this enigmatic figure has an agenda of his own…