Reborn three days before a volcanic heat apocalypse, Nova rushes to warn the biological parents she just found, only to discover they want her gone forever. To protect their beloved adopted daughter, Sable, they follow an online trick and lock Nova inside an underground bunker built as her prison. But Nova plays along, forcing them to reinforce the shelter with heatproof alloys and stock it with three years of supplies. They think they buried the real daughter alive. They never imagined the world would burn, and the cage they built to destroy her would become sanctuary to outlive them all.