Where can you hide when you're running from yourself? Catarina thought they had stopped the Hydra virus. She was wrong. After laying everything on the line to decrypt the vaccine, Cat realizes that Lachlan's daemon code is in the panel of every person on the planet. With it, he can reprogram humanity. She, Cole, and Leoben set out to stop him, but they're on a timer. Cartaxus, the shadowy corporation that's both helped and hindered them, has a deadly endgame in play. The virus is evolving, the vaccine is dying, and if Cat can't find Lachlan in three days, they'll use lethal code to wipe out everyone. Their path takes them to Entropia, an underground city deep in the desert and home to the most extreme gene hackers, run by the queen of coding, Regina. Struggling with the revelations about her past and plagued by strange visions, what Cat finds in Entropia is more than just a trail to Lachlan.