There have been a series of strange murder cases in Tianhai City. The deceased were all killed with a single knife, in the middle of the heart, and had black iris tattoos on their necks. The deceased were all persons with supernatural powers during their lifetime. Suspended detective Ji Linyuan was involved in the case because of a mysterious obsidian badge - the badge can copy the superpowers of the deceased, but will gradually erode his consciousness, leading him to the fate of "blackening the stand-in".
