Professional assassins Lynn (Shu Qi) and Sue (Zhao Wei) are two sisters who own World Panorama, a state-of-the-art surveillance system. Hired by Chow Lui to investigate a virus, Lynn kills the wealthy computer magnate with cyanide-loaded sunglasses. Assigned to solve the murder is Kong Yat Hong (Karen Mok), an ambitious undercover cop, who learns Chow Nunn, Lui's brother, hired Lynn. To cover his tracks, Nunn plans to send Sue after Hong, and then wipe out both siblings. Lynn tries to save her sister, but arrives too late. Joining forces with Hong, Lynn takes on Nunn's men in a martial arts battle to the death.