The growing threat of the Weird has driven the Expansion to paranoia and oppression. Mandatory testing for infection is introduced, and the colony Braun's World - following reports of a new portal opening - is purged from orbit, at an unimaginable cost in lives.

Delia Walker, a senior analyst in the Expansions's intelligence bureau, protests the new policies and is drummed out. Desperate for a sign of hope, she charters the decrepit freighter the Baba Yaga and heads into Satan's Reach, following rumours of a world where humans and the Weird live peacefully side by side.
Hunted by the Bureau, Walker, her pilot Yershov, and Failt – a Vetch child stowaway, fleeing slavery – will uncover secrets about both the Weird and the Expansion; secrets that could prevent the seemingly inevitable war...