After Lin Shiyao’s arrest, Lei Yiming is inspired by policeman Wu De to reopen an old case of Lin’s from many years ago. Ten years ago, Lin was working on the case of a drug cartel. His friend was undercover, and was killed by friendly fire in an attack lead by Lin. Lin had felt guilty for many years, and had taken care of his friend’s son as he grew up. Surprisingly, the deceased in the current shootings were all involved in that old drug cartel! CSIC’s unrelenting investigation reveals that the killer knows Lin well, and that Lin’s wife will be the last target for his revenge.