'P' fung bou

William Luk (Louis Koo) goes undercover in prison as a DUI charge to investigate prison officers accepting bribes from rich heir Cho Yuen-yuen (Raymond Lam), who murdered Luk's former high school principal. Luk is aided by his colleague Kenny Ching (Kevin Cheng) and friend Joint Financial Intelligence Unit officer Lau Po-keung (Julian Cheung) from the outside. Luk must navigate a treacherous prison landscape led by former superintendent Wong Man-ban (Gordon Lam), while also confronting his past and Wong's personal vendetta against him.