LAM TING-TING gets injured while trying to save an old lady, in the course of which she happens to discover a dreadful murder of four members of the same family. Senior Chemist of the Forensic Science Division KO YIN-POK arrives at the scene. From the bloodstains on the ground he infers that there is still at least a survivor. TING admires him so much for his intelligence and extraordinary powers of observation. Senior Inspector LEUNG SIU-YAU, who has been newly transferred to the Regional Crime Unit, believes that the murderer was aiming for the diamonds kept in the house owner TAM TAK’s safe. POK tries to catch up with the garbage truck to look for the murder weapon. YAU checks out the registration number of the truck and informs POK immediately. POK finally manages to find a knife and some other evidence in the refuse dump. YAU follows Forensic Pathologist KOO CHAK-SUM to the mortuary for the autopsy.… ...

SUM points out that they have to keep a clear head to make a fair judgment while looking for the murderer, and YAU is finally convinced. TSAU claims that he was involved in a car theft when the murder took place, which is proved to be true after YAU’s investigation. YAU blames the owner of the stolen car for putting up with the thieves again and again. KOO CHAK-YIU, POK’s wife and SUM’s elder sister, was paralyzed in a car crash years ago. POK and SUM are astonished to hear that YIU is suffering from liver cancer. SUM used to be a problem teenager but YIU’s desperate attempt to save him touched him deeply and changed his whole life. SUM feels so sorry for YIU and wonders why fate is so cruel to her. POK cannot do anything but give him a few words of consolation. SUM discovers that the murderer has been hiding something. Immediately he goes and explains to YAU his views and analysis.… ...