Chuckling is judged guilty of murdering gang lord Michael So and also is sentenced to life jail time. Secured behind bars, he fulfills the seemingly benign inmate Fok Tin Yam, an university teacher in criminal psychology who is incarcerated for drug ownership. Very intelligent and manipulative, Fok discloses the power of his mind games by easily suppressing the fierce prison bully. He additionally deduces that Giggling is sent out to the jail on a covert mission to find out the rogue police officers within the police. The ideas lead him to prisoner Chit, a former sergeant from the Narcotics Bureau who has been suffering from a mental disorder. To open the important details from the mad male, Laughing have to get the aid of Fok, yet this enigmatic figure has a schedule of his own ...