Lucy has grown up in a cave. Not as a prisoner — as a student, under the care of a monk whom she calls Father Roshi. Roshi calls her Lu-See and has shaped her perception of the world from the inside out and she sees without categories, to feel without defences. She does not know what she is about to walk into.

Six is a professional operative with a condition that renders him incapable of physical pain. He has built a career on the edge of that absence. What he feels instead is something harder to name.

Across the roof of the world, two lives are moving toward collision — tracked by forces that view children as cargo, and by governments that view borders as weapons. What neither Lucy nor Six can know is what finding each other will cost them.