Many cases have been solved because of Shan's integrity as a police officer. When his sting operation is targeted by a mystery bunch of criminals, lead by Ngo, his former protégé, his past comes back to haunt him. Ngo was formerly a very skilled police officer who really respected Shan. Nevertheless, he was taken to prison three years ago after a tragic injury transformed him into an angry man determined to kill everybody who has offended him.