A missing police pistol is connected to a series of recent heists and murders. Its owner, Wong, vanished while pursuing suspects in the mountains, yet his partner, Chi-Wai, miraculously returned unharmed. Hotshot inspector Ho (Andy On) is in charge of the investigation, but Ho knows his only chance of cracking the case lies in enlisting the help of Bun (Lau Ching Wan), the reclusive yet gifted mad detective."