Arato Endou and his hIE companion, Lacia, reunite to demonstrate that shutting down powerful AIs can be accomplished safely. As they venture into a holding center to confront Lacia's creator, Higgins, they must confront various adversaries. Snowdrop, a rogue hIE, is determined to consume Higgins, while Methode, another hIE, seeks vengeance against Lacia. The planet's most intelligent AIs unanimously agree to terminate Lacia, believing her to be a threat to humanity. With time running out and the cards stacked against them, can Arato and Lacia bridge the gap between people and hIEs to create a peaceful co-existing society?