PO fights off a female assassin. Before she leaves, she swears to return to revenge him. PO is puzzled. FUNG is going to a fishing village to investigate the death of PRINCE TSUN. SAM goes with him. The memory of how FUNG took explosive out of a fish comes back to him. He therefore believes he has killed PRINCE TSUN. PO is going out with YEUNG when the female assassin comes again. It turns out that her name is SHAREN GAOWA and that she is the daughter of the Mongol PO and YEUNG arrested earlier. For fear that he has made a mistake, he goes to the prison with GAOWA. TAI visits LADY UNG. He did not know until then that she fell into a river lately and SAM saved her. FUNG has found a jade ring. He also discovers that he used to go to Yuet Loi Inn regularly to pick up confidential letters. He suspects he is a killer.