YEE and YUNG check the old file. They find out that the victim named MEI. She committed suicide a year ago together with her boyfriend, HON, who is a foreigner. YEE and YUNG inspect the satchel. They discover a letter which was written by MEI to FUNG (who had died 5 years ago). It depicts how they were persecuted by Butterfly. YEE and YUNG even receive a call front MEI’s spirit. She implores them to clear the case for her. They find out that both FUNG and HON did have an affair with a rich lady, TING, who has married.FUNG is the member of the Butterfly Club. He had been fallen in love with TING. FUNG had fell down from a cliff and died five years ago when he tried to catch a butterfly. HON is TING’s subordinate. CHIT is asked to investigate TING. YEE and YUNG go to MEI's school for some hints. They find out that MEI and CHIT are classmates. CHIT's plot is unveiled.

CHIT tells them that MEI was killed by TING as she has an affair with ON (TING’s husband). YEE and YUNG does not believe CHIT’s words. They further investigate. They apply for reading MEI and HON’s coroner’s report. They find out that MEI and HON had taken too much sleeping pills. Besides, MEI was strangled by a tie and HON hanged himself on the tree. The spot was a villa belonged to Hon's good friend. HON always went there with a mature lady. Moreover, a child states that MEI was a new face to him and she rarely went there. This indicates that MEI is not HON's real girlfriend. Moreover, LAI had also been to Japan five years ago. It is claimed that FUNG tried to catch a special butterfly and unfortunately fell down from the cliff. TING is the only witness. However, LAI finds out that the kind of special butterfly had already extinct as the kind of special bean which those butterflies depended on was in shortage.

YEE and YUNG read TING’s testimony. They find out that the day they died was her wedding anniversary. ON is the only time witness for TING. He proves that he was with TING to celebrate their anniversary. KEE (TING’s secretary) Stated that HON had called TING a several times that day. He lost his temper and claimed that TING had cheated him. YUNG finds a picture painted a butterfly with the help from a villa keeper. HON had once wanted to give it to a friend but he kept it for himself at the end. YUNG discovers the alphabet‘ J4E’ from the picture. He even knows that HON likes to sleep on a hanging bed. The child from the village picks sonic tore off pieces of the hanging bed. They reckon that TING and HON were secret lovers. TING sets a plot to destroy the two so as to maintain her reputation.

YEE and YUNG do not have enough time to appeal. CHIT does not give up. She meets ON when she is visiting MEI’s tomb. She follows him and finds that he had secluded in a villa at the suburban area. CHIT dresses herself up similar to MEI in order to win ON's favour. She soon becomes ON’s friend and wins his trust. She finds that TING killed the two was out of jealousy. She married ON for the sake of wealth. ON and TING do not love each other. Till ON meets MEI he finds real love. ON was made drunk by TING on that night. YUNG has no courage to disclose the truth. CHIT pretends to be MEI’s spirit and writes letter to TING. She claims that she will take revenge. She even sends TING the small piece of HON’s hanging bed.