The nightmare of the outbreak is finally over, but Cat's fight has only just begun.

Exhausted, wounded, and reeling from revelations that have shaken her to her core, Cat is at a breaking point. Camped in the woods with Cole and Leoben, she's working day and night, desperate to find a way to stop Lachlan's plan to reprogram humanity. But she's failing--Cat can't even control her newly regrown panel, and try as she might to ignore them, she keeps seeing glitching visions from her past everywhere she turns.

When news arrives that the Hydra virus might not be as dead as they'd thought, the group is pushed into an uneasy alliance with Cartaxus to hunt down Lachlan and fix the vaccine. Their search takes them to Entropia, a city of gene-hackers hidden deep in the desert that could also hold the answers about Cat's past that she's been searching for.

But when confronted with lies and betrayals, Cat is forced to question everything she knows and everyone she trusts. And while Lachlan is always two steps ahead, the biggest threat to Cat may be the secrets buried in her own mind.