Harold and Echika may have brought their latest case to a close, but the developer of the AI who facilitated E's campaign against Interpol is nowhere to be found. To ascertain the identity of this enigmatic individual, the pair request the aid of their friend Bigga, now a formal consultant with the Electrocrime Investigation Bureau. Yet even her help isn't enough to give them a lead. Meanwhile, a series of spree killings against Amicus begin to unfold, and the modus operandi bears an eerie resemblance to the murder of Harold's mentor...