Ko (Chow) is an undercover cop on one last job, assigned to infiltrate a gang of jewel thieves committing armed robberies across Hong Kong. When another police officer is killed in the line of duty during one of the gang's heists, Ko finds himself caught in the crossfire between the police force desperate to catch the culprits at any cost, and the trigger-happy thieves who begin to smell a rat in their midst. As the bullets fly and the body count rises, Ko's only hope for survival might be his burgeoning friendship with weary gang member Fu (Danny Lee)...