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…

Detective Johnny Du was smart and agile but his height of 5 feet 4 has hindered him from joining the G4 protection detail for the Chief Executive. His sassy girlfriend Angel bullied him all the time, leaving him depressed at work and at home. His helplessness attracted Vincent, the Devil Prince and Jim, the Angel to fight for his soul.

A cop and his team of comrades go undercover in one of China’s most ruthless underworld organizations to stop a gang leader, only to put themselves in great danger after being exposed one by one.