Ella Patel - thief, con-artist and smuggler - is in the wrong place at the wrong time. One night, on the border of a demilitarised zone run by the body-swapping alien invaders, she happens upon a man and woman being chased by a group of assailants. The man freezes, leaving the woman to fight off five attackers at once, before succumbing. As she dies, to both Ella and the man's surprise, the sparkling light that rises from the woman enters Ella, instead of the man. She soon realises she's been inhabited by Io, a low-ranking Quasing who was involved in some of the worst decisions in history. Now Ella must now help the alien presence to complete her mission and investigate a rash of murders in the border states that maintain the frail peace.