In 1980s Hong Kong, troubled youth Chan Lok-kwun, a mainland refugee, struggles to survive in the Kowloon Walled City by joining underground fights. Betrayed by crime boss Mr. Big while trying to buy a fake ID, he steals drugs from him and seeks refuge in the Walled City, where he encounters Cyclone, a compassionate yet authoritative crime lord.
Veteran detective Cham works with rookie cop Will to hunt down the city's serial killer. The investigation leads them to a lair littered with dismembered female limbs, and an ex-con who killed Cham's wife and child years ago...
A computer expert accidentally falls into the conspiracy of online financial crime and has to seize the time to participate in the struggle.
